FTS: Failover/rebalance/add-back does not cleanup indexes

Build: 7.0.0 build 5251

• Create a 2 node cluster with kv and fts on each node
• Load travel-sample
• Create a default index on travel-sample with 1 partition
• Failover and rebalance search node
• Note that pindex files not cleaned in failed over node
• Now drop the bucket travel-sample
• Add-back same search-node with search service.
• We see the indexes created before failover still exists even without source bucket

Logs:

https://cb-jira.s3.us-east-2.amazonaws.com/logs/failover/collectinfo-2021-06-02T022804-ns_1%40172.23.97.211.zip
https://cb-jira.s3.us-east-2.amazonaws.com/logs/failover/collectinfo-2021-06-02T022804-ns_1%40172.23.97.212.zip