fix DXCron, lockout and close_gracefully

1. Fix DXCron::spawn_cmd so that more than one spawn_cmd can be active at a
   time. This affects many nodes where lots of regular spawn_cmds happen at
   a time and this prevented crucial things like 'start_connect' from working!
2. Sort user lockout issues to cope with all likely scenarios - including
   "phantom" SSID working.
3. Fix "close_gracefully" error messages which are useless, but benign. These
   happen (mainly) when outgoing connects timeout.