bucket_engine is a part of memcached

Change-Id: I0557210ed9ca54297afebb890a25e4deb7b5d85c
Reviewed-on: http://review.couchbase.org/26858
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>