make sure that uninhibit doesn't wait for all vbuckets to be compacted

... in case of non-parallel index compaction

Change-Id: Ifd028edd45edb1f22f3dd56d21e4f3a6f5ccad52
Reviewed-on: http://review.couchbase.org/39395
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>