MB-9955: Don't check opaque when closing a stream

Since the close stream command can only be sent over the same
connection that the stream is on we don't need to check the
opaque since ther is only one stream per vbucket.

Change-Id: Ia7086fe5385b12fed7b7520425e3e5031616b4c9
Reviewed-on: http://review.couchbase.org/33235
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>