MB-12497 Improve Error Handling For Index Build

If Initial Index Build request fails, mark the index state as Error,
so next index requests can be processed.

Change-Id: I13fd39f62f6d22beed3824b1a052dc860773f629
Reviewed-on: http://review.couchbase.org/43526
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Tested-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>