Server side can enforce auth while client skips it

Steps to reproduce:

1. Set-up a 3 node cluster: 1 KV + n1ql, 2 index nodes on 7.0.5 version

2. Create an index with replica

3. Failover one indexer node

4. Restart cbq-engine. Scan will fail with "No index available" error

As there is a not failed over, the internal version at client will be set to empty string and client will skip the auth. On server side, server will enforce the auth as internal version is reached from server.