src/pmlogger/pmlogger_daily.sh: fix diagnostic spaghetti
src/pmlogger/pmlogger_daily.sh: fix diagnostic spaghetti

With -VV, _get_non_primary_logger_pid() was writing a mix of pids and
"helpful" diagnostic messages on stdout, which led to interesting
results when pmkill was called to send SIGHUP to all the "pids"
in the stdout from _get_non_primary_logger_pid()!

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