This is a xen guest ("dupontx" on "airbus").  On boot up, syslog-ng does not
start correctly:

# systemctl status syslog-ng
syslog-ng.service - System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/syslog-ng.service; enabled)
   Active: failed (Result: start-limit) since Mon 2015-03-09 09:31:30 CET; 1min
6s ago
  Process: 453 ExecStart=/usr/sbin/syslog-ng -F $SYSLOG_NG_PARAMS (code=exited,
status=2)
  Process: 448 ExecStartPre=/usr/sbin/syslog-ng-service-prepare (code=exited,
status=0/SUCCESS)
 Main PID: 453 (code=exited, status=2)

Mar 09 09:31:30 dupont8 systemd[1]: syslog-ng.service: main process exited,
code=exited, status=2/INVALIDARGUMENT
Mar 09 09:31:30 dupont8 systemd[1]: Unit syslog-ng.service entered failed
state.
Mar 09 09:31:30 dupont8 systemd[1]: Starting System Logging Service...
Mar 09 09:31:30 dupont8 systemd[1]: syslog-ng.service start request repeated
too quickly, refusing to start.


After I've logged in, starting it manually works fine.  I've added arguments
"-v -d -e" to the syslog-ng startup, but they don't seem to produce any more
debug output.