Send LCB_CONNECT_ERROR, not LCB_UNKNOWN_HOST for connection failures

UNKNOWN_HOST should only be delivered when getaddrinfo() fails.

Change-Id: I32ade7c7de2e0d86a41d49bb7beb2bd9cfbeab83
Reviewed-on: http://review.couchbase.org/41392
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>