CV Intermittent test: Timeout in CompactAndScan/magma

As seen during unit-simple-test, suite times out after 5mins:

Note: Google Test filter = KVStoreParam/KVStoreParamTest.*

[==========] Running 111 tests from 1 test suite.

[----------] Global test environment set-up.

[----------] 111 tests from KVStoreParam/KVStoreParamTest

[ RUN      ] KVStoreParam/KVStoreParamTest.BasicTest/magma

[       OK ] KVStoreParam/KVStoreParamTest.BasicTest/magma (23 ms)

...

[ RUN      ] KVStoreParam/KVStoreParamTest.CompactAndScan/magma

<TIMEOUT>

Preceding tests appear to complete in <1min, so looks like CompactAndScan/magma is timing out after ~4mins.

First seen during http://cv.jenkins.couchbase.com/job/unit-simple-test/33629/ (0.0.0-2380 on Ubuntu20.04), also seen in the subsequent 2381 run (http://cv.jenkins.couchbase.com/job/unit-simple-test/33643/) so this seems quite repeatable in that environment.

Note it wasn't observed in the CentOS7 variant of those two builds - full history here: http://cv.jenkins.couchbase.com/job/unit-simple-test/33643/testReport/junit/projectroot/kv_engine/ep_engine_ep_unit_tests_KVStoreParam_KVStoreParamTest/history/

Interestingly no changes to kv-engine or magma within that build range (http://changelog.build.couchbase.com/?product=couchbase-server&fromVersion=0.0.0&fromBuild=2380&toVersion=0.0.0&toBuild=2381&f_asterixdb=on&f_couchdb=on&f_goxdcr=on&f_ns_server=on&f_product-metadata=on&f_query-ui=on), so not clear why it's recently started occurring...