One-to-one mapping fallback between "via" interface and "base" interface.

[tedlean]

When establishing an interface, the forwarder makes a lookup in a configMap to find the mapping between the name of the interface to create and the name of the host interface to use. This way the host interface can be reached "via" one or more interface name aliases. If the name of the interface to create cannot be found in the list of "via" aliases the interface will not be create.

This means that ConfigMap very often have to be adapted to the actual cluster environment, also in the most normal case where the mapping simply is one-to-one, like eth5 via eth5.

The proposal is to extend the current functionality to first look in the configMap as of today, but if not found here, simply try to use a one-to-one mapping as a fall-back.