discover/network: Add find_interface_by_uuid

Currently in network_register_device() and network_unregister_device()
the appropriate interface is searched for by name. However it is
possible in some scenarios for multiple interfaces to have the same
name, so instead search by UUID to be sure that the correct interface is
being selected.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>