redirect stderr of find command to /dev/null

reduce warnings messages in some situation，eg，non-privileged user build with --libs=/usr/lib64

add redis auth.

add auth failed log.

tag with_auth in Socket::WriteRequest.

add ut.

fix redis port.

mv REDIS_AUTH_FLAG from Controller to Socket.

change MAX_PIPELINED_COUNT from 65536 to 32768.

we met some weird bug

support PLAIN authentication of couchbase in memcache client