ING-1495: When creating/dropping a primary idx, call consistency helpers with '#primary'

[DemetrisChr]

After creating a primary index with no custom name (i.e. the name is #primary), EnsureQueryIndexCreated is called with the empty string as the name, instead of setting it to #primary. This means that the EnsureQueryIndexCreated call, and the overall CreatePrimaryIndex RPC call, don't return, until timeout.

[Westwooo]

@DemetrisChr nice catch, would you be able to add a test case to TestQueryManagement in gateway/test/query_mgmt_test.go that covers this case (where the primary index name is nil)?

[DemetrisChr]

@DemetrisChr nice catch, would you be able to add a test case to TestQueryManagement in gateway/test/query_mgmt_test.go that covers this case (where the primary index name is nil)?

I've added a test. I wanted it to be as exhaustive as the ones for the named primary index, but it wasn't straightforward to make the individual tests isolated, because they all operate on the same index. So I've added a simpler test that verifies that the index can be dropped and created.

I've also spotted that DropPrimaryIndex had the same issue, although in that case it meant that EnsureQueryIndexDropped wasn't ensuring that the index was dropped, rather than getting stuck indefinitely. I've updated that as well.