teuthology/task/selinux: ignore denials in agetty
This was tracked in [1], but the addition of the context to the
allowlist in ceph.git commit
7a6389272aff ("qa: ignore container
checkpoint/restore related selinux denials for centos9") doesn't
cover krbd suite which doesn't pull in any distro snippets.
Since this denial has nothing to do with Ceph [2], let's ignore it
globally.
[1] http://tracker.ceph.com/issues/64616
[2] https://bugzilla.redhat.com/show_bug.cgi?id=
2259622
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>