selftests: add selftest for chaining of tc ingress handling to egress

This test runs a simple ingress tc setup between two veth pairs,
then adds a egress->ingress rule to test the chaining of tc ingress
pipeline to tc egress piepline.

Signed-off-by: Paul Blakey <paulb@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>