Merge branch 'selftests-forwarding-Tweaks-and-a-new-test'

Ido Schimmel says:

====================
selftests: forwarding: Tweaks and a new test

First patch adds a new test for VLAN-unaware bridges.

Next two patches make the tests fail in case they are missing interfaces
or dependencies.

Last patch allows one to create the veth interfaces even without the
optional configuration file.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>