nm_device_connection_match_config() sounded more generic than it
really was; rename it to nm_device_find_assumable_connection(), which
is what it really does.

There was also a lot of redundancy/cut+paste in the subclass
implementations of connection_match_config(); Improve things by moving
the looping-over-connections code into NMDevice itself, and also doing
the general-device-compatibility and IP-config checking there, leaving
the device subclasses to just verify L2 properties. Which most of them
aren't doing...

https://bugzilla.gnome.org/show_bug.cgi?id=693684