[YCQL] Index tables treated as created before tablets created.

[mheer9]

Jira Link: DB-817
'ImportSnaposhot' calls CatalogManager::CreateTable (for YCQL).

Master treats index tables as created before we create the tablets.
If the tablets fail to create i.e. backpressure, timeouts, these tablets can be replaced, leading to inconsistent tablet-ids when using yb-admin import_snaposhot.

Create Table should just fail in such cases.

[m-iancu]

@mheer9 Do you know (remember) if this could affect the regular backup/restore flow or does it only come up if we run import_snapshot manually?