MB-19677 Return memcached errors from quick_stats.
MB-19677 Return memcached errors from quick_stats.

Change-Id: I1afc7d81aa7616cf23eb2b1165d7e4705253f7f2
Reviewed-on: http://review.couchbase.org/64346
Tested-by: Aliaksey Artamonau <3c875bcfb3adf2a65b2ae7686ca921e6c9433147@gmail.com>
Reviewed-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>

ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,ceejatec/ns_server,membase/ns_server,ceejatec/ns_server,ceejatec/ns_server,membase/ns_server