ipatests: Don't assume sshd flush its logs immediately
sshd logs are not displayed immediately in journalctl, this results
in the tests checked the corresponding system logs are racy. I can't
find a way to flush ones. So, the best is the periodical reading of
the system log.
Related: https://pagure.io/freeipa/issue/8682
Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Sergey Orlov <sorlov@redhat.com>