CCBC-279: lcb_wait() should always return success

Change-Id: I7d09a982c8a17efffcb618dc2e9704bb287ad5f1
Reviewed-on: http://review.couchbase.org/29458
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>