FTS: Partition rebuilds during failover/addback on one of the node

Build: 7.0.0-4788

Found partitions rebuild on one of the node while validating the issue: MB-41113
Test steps:

1. Setup a cluster with 2 kv+n1ql and 5 index+fts nodes
2. Create a bucket with 250000 items
3. Create 3 fts indexes:
4. one with 1 replica and 10 partitions
5. sencond with 1 replica and 17 partitions
6. third with 2 replica and 25 partitions
7. Now failover/ addback and rebalance each node (kv nodes first)

Seems like partitions on node: 172.23.107.197 did rebuild.

Cluster config:

172.23.107.197:8091 => 'services': [u'fts', u'index']}

172.23.107.104:8091 => 'services': [u'kv', u'n1ql']}

172.23.107.87:8091 => 'services': [u'fts', u'index']}

172.23.121.46:8091 => 'services': [u'fts', u'index']}

172.23.121.45:8091 => 'services': [u'fts', u'index']}

172.23.106.245:8091 => 'services': [u'kv', u'n1ql']}

172.23.121.41:8091 => 'services': [u'fts', u'index']}

Logs attached