CI tests disabled

From: Warner Losh <imp_at_bsdimp.com>
Date: Thu, 16 Dec 2021 01:43:28 UTC
The following CI tests have been failing for a while (weeks?). I've
disabled them in CI and filed bugs.

sys.net.if_bridge_test.span
sys.netpfil.pf.forward.v6
sys.netpfil.pf.set_tos.v6
sys.netpfil.pf.killstate.v6

https://bugs.freebsd.org/260461
https://bugs.freebsd.org/260460
https://bugs.freebsd.org/260459
https://bugs.freebsd.org/260458

Feel free to re-enable them after they are working in CI again.

Warner