Only set local_port and local_address for tcp

This seems to fix #181 for me while using a unix socket as the Docker.url.
This should also match against http and https similar to here: https://github.com/swipely/docker-api/blob/88b2739c8edd3812bb716c1daeb77629cdddfac3/lib/docker/connection.rb#L21 , right?