Add use case section to fcnal-test.
Initial test is VRF based with a bridge and vlans. The commands
stem from bug reports fixed by:
a173f066c7 ("netfilter: bridge: Don't sabotage nf_hook calls from an l3mdev")
cd6428988b ("netfilter: bridge: Don't sabotage nf_hook calls for an l3mdev slave")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>