Temporarily skip sys.geom.class.multipath.failloop.failloop in CI

This test case uses dtrace -c but it has some issues at the moment so
disable it until dtrace fixed.

From markj:

This is the CTF type ID limit which has come up quite a few times
lately. It'll be fixed with the introduction of CTFv3.

PR: 258763
Sponsored by: The FreeBSD Foundation