test: replace journal checkers with journalctl --follow + grep -m

test: replace journal checkers with journalctl --follow + grep -m

Recently, for slow test environments, journalctl --sync was added to the
loop in the timeout. However, journalctl --sync may be slow in such systems,
and timeout easily triggered during syncing.
Hopefully, reading journal with --follow and grep the output with an expected
line should be efficient.

Hopefully fixes #32712.