qa/023: re-enable pmlogger service correctly on non-systemd platforms
qa/023: re-enable pmlogger service correctly on non-systemd platforms

qa/023 was unconditionally disabling pmlogger and then only
re-enabling it in cleanup() if _need_clean was true. This only
seemed to affect non-systemd platforms but was causing 023,
025, 032 and 041 to subsequently fail due to messages about
the pmlogger service not being permanently enabled.

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