transfer_socket: Don't perform checks if to==from

We should return when we detect the connections are idential, as the
assertions are only for actual transfers

Change-Id: Ia9ba0cc40df3c7bc494ff445c3a0c2daaaf946c3
Reviewed-on: http://review.couchbase.org/33111
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>