MB-11365:Datatype to be in response where required

- Return datatype in responses for GAT, GATQ,
  GetLocked, GetRandomKey

Change-Id: Ia7e40c7d4a79efae3f9cfff41b51d099e89b0621
Reviewed-on: http://review.couchbase.org/38078
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: abhinav dangeti <abhinav@couchbase.com>