qa/common.check: fix cut-n-paste error in journalctl use
qa/common.check: fix cut-n-paste error in journalctl use

When systemd is in play, this was (recently) broken for
    _service <op> foo
for any foo other than "pcp" or "pmcd".

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp