Make default ANSIBLE_REMOTE_PORT None

The ansible remote port should be None, not 22. Having a default value
of 22 means that '-o Port 22' will be appended to the ssh connection
all of the time. This is incorrect as when one would like to use
something like an ssh configuration file (-F) that sets the port to
something other than 22.

Part of this change requires that we check that, in get_config, the
value is not None before trying to cast it into an integer or float.