Check if the send buffer is full or not for an DCP mutation.
Check if the send buffer is full or not for an DCP mutation.

Change-Id: I4401cda9b16ced3278f505169ed1f4658e18dcfa
Reviewed-on: http://review.couchbase.org/40397
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

couchbase/memcached,couchbase/memcached,daverigby/kv_engine,cloudrain21/memcached-1,daverigby/memcached,daverigby/kv_engine,owendCB/memcached,jimwwalker/memcached,owendCB/memcached,couchbase/memcached,couchbase/memcached,daverigby/memcached,mrkwse/memcached,cloudrain21/memcached-1,jimwwalker/memcached,jimwwalker/memcached,owendCB/memcached,cloudrain21/memcached-1,mrkwse/memcached,owendCB/memcached,cloudrain21/memcached-1,daverigby/kv_engine,daverigby/memcached,mrkwse/memcached,mrkwse/memcached,daverigby/memcached,daverigby/kv_engine