Add more tests.

1. Check that toggling forwarding deletes autoconf routes in
   all tables.
2. Add a test for Path MTU discovery (IPv6 only for now).
3. Add a test that checks that there are no leftover routes on
   routing table switch. Currently disabled, because there's no
   way to delete routing tables in Linux.

Change-Id: Ie21a2d2c14304d9c0fb7cd688b90cb8715e0bd68
1 file changed