scanner: Add query request status log message

Change-Id: I939acdcbd965ed5e2c50eceaad5bdfc77cca7f79
Reviewed-on: http://review.couchbase.org/43478
Reviewed-by: Deepkaran Salooja <deepkaran.couchbase@gmail.com>
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Tested-by: Sarath Lakshman <sarath@couchbase.com>