Always check opaque in upr consumer response handler

Change-Id: I0912d5615c8297a1b921205837b70e40a4f29f39
Reviewed-on: http://review.couchbase.org/36553
Reviewed-by: Sundararaman Sridharan <sundar@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>