Leak due to verbose logging MultiScanInternal()

During the analysis of MB-43070, we encountered a query OOM as follows:

cbcollects:

url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.106.134.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.106.136.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.58.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.73.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.74.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.75.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.77.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.81.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.120.86.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.121.77.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.24.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.25.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.26.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.31.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.32.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.123.33.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.122.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.14.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.18.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.243.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.254.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.96.48.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.105.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.110.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.112.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.149.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.150.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.151.zip
url : https://cb-jira.s3.us-east-2.amazonaws.com/logs/systestmon-1608351004/collectinfo-2020-12-19T041007-ns_1%40172.23.97.74.zip

Query nodes are 172.23.97.148 & 149.

On inspection of query node 149, this is where memory goes:

(pprof) lines
(pprof) top
Showing nodes accounting for 9.81GB, 98.02% of 10.01GB total
Dropped 462 nodes (cum <= 0.05GB)
Showing top 10 nodes out of 28
flat flat% sum% cum cum%
9.58GB 95.71% 95.71% 9.58GB 95.72% github.com/couchbase/indexing/secondary/queryport/client.(*GsiClient).MultiScanInternal /home/marco/query/src/github.com/couchbase/indexing/secondary/logging/logging.go:297
0.09GB 0.9% 96.61% 0.09GB 0.95% [cbq-engine]
0.08GB 0.75% 97.35% 0.08GB 0.75% strings.Map /usr/local/go/src/strings/builder.go:40
0.07GB 0.67% 98.02% 0.07GB 0.67% github.com/couchbase/gometa/protocol.createConnection /home/marco/query/src/github.com/couchbase/gometa/protocol/followerServer.go:220
0 0% 98.02% 0.07GB 0.67% github.com/couchbase/gometa/protocol.createConnection /home/marco/query/src/github.com/couchbase/gometa/protocol/followerServer.go:218
0 0% 98.02% 0.07GB 0.67% github.com/couchbase/gometa/protocol.syncWithPeer /home/marco/query/src/github.com/couchbase/gometa/protocol/discovery.go:852
0 0% 98.02% 0.06GB 0.59% github.com/couchbase/indexing/secondary/manager/client.(*watcher).updateServiceMap /home/marco/query/src/github.com/couchbase/indexing/secondary/manager/client/metadata_provider.go:5084
0 0% 98.02% 0.06GB 0.63% github.com/couchbase/indexing/secondary/planner.(*IndexerConstraint).CanAddIndex /home/marco/query/src/github.com/couchbase/indexing/secondary/planner/planner.go:3519
0 0% 98.02% 0.06GB 0.63% github.com/couchbase/indexing/secondary/planner.(*RandomPlacement).findLeastUsedAndPopulatedTargetNode /home/marco/query/src/github.com/couchbase/indexing/secondary/planner/planner.go:5340
0 0% 98.02% 0.06GB 0.63% github.com/couchbase/indexing/secondary/planner.(*SAPlanner).DropReplica /home/marco/query/src/github.com/couchbase/indexing/secondary/planner/planner.go:659
In particular, the memory goes in this bit of logging:

https://github.com/couchbase/indexing/blob/dec9e932a90e3339eb787d317609dfac2a281b85/secondary/queryport/client/client.go#L909

The verbose formatting placed in a local variable causes the string to be allocated on the heap, because the variable is passed higher up the stack.
Lazy logging would help in this case, or at least pass the constant directly to logging.Verbosef().