[Upgrade]: CommitSyncWrites written by pre-7.1 using V3 metadata are not deserialised correctly

Scenario:

• 3 node cluster (6.6.4-9961), three couchbase buckets
• Data loading running in background
• Upgrade nodes to 6.6.5-10068 one by one
• Enable e2e encryption on the cluster

  $] curl -v -u Administrator:password -X POST http://localhost:8091/internalSettings -d "canEnableStrictEncryption=true"

  $] /opt/couchbase/bin/couchbase-cli node-to-node-encryption -c http://localhost:8091 -u Administrator -p password --enable

  $] curl -v -u Administrator:password http://localhost:8091/settings/security -d "clusterEncryptionLevel=control"

• Cluster upgraded to 6.6.5 successfully
• Failover one of the node and perform upgrade to 7.1.0-2017 build using, 

  rpm -U couchbase-server-enterprise-7.1.0-2017-centos7.x86_64.rpm

• Perform "Delta add back" of the node back to the cluster and trigger rebalance

Observation:

Bucket b2 and b3 completes warmup. Bucket "b1" warmup hangs.