systemctl: return diffrent error code if service exist or not (#3385)

systemctl: return diffrent error code if service exist or not (#3385)

Before:
[sus@maximus bz-1256858]$ systemctl status rsyslog.service;echo $?
● rsyslog.service - System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor
preset: enabled)
  Drop-In: /etc/systemd/system/rsyslog.service.d
           └─50-CPUShares.conf
   Active: inactive (dead) since Mon 2016-05-30 11:54:25 IST; 2h 26min ago
     Docs: man:rsyslogd(8)
           http://www.rsyslog.com/doc/
  Process: 1159 ExecStart=/usr/sbin/rsyslogd -n $SYSLOGD_OPTIONS (code=exited,
status=0/SUCCESS)
 Main PID: 1159 (code=exited, status=0/SUCCESS)

May 30 11:07:50 maximus systemd[1]: Starting System Logging Service...
May 30 11:07:50 maximus systemd[1]: Started System Logging Service.
May 30 11:54:25 maximus systemd[1]: Stopping System Logging Service...
May 30 11:54:25 maximus systemd[1]: Stopped System Logging Service.
3
[sus@maximus bz-1256858]$ systemctl status hello.service;echo $?
● hello.service
   Loaded: not-found (Reason: No such file or directory)
   Active: inactive (dead)
3

After:
$ ./systemctl status hello.service;echo $?
Failed to dump process list, ignoring: Access denied
● hello.service
   Loaded: not-found (Reason: No such file or directory)
   Active: inactive (dead)
4
[sus@maximus bz-1256858]$  ./systemctl status rsyslog.service;echo $?
Failed to dump process list, ignoring: Access denied
● rsyslog.service - System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor
preset: enabled)
  Drop-In: /etc/systemd/system/rsyslog.service.d
           └─50-CPUShares.conf
   Active: inactive (dead) since Mon 2016-05-30 11:54:25 IST; 2h 24min ago
     Docs: man:rsyslogd(8)
           http://www.rsyslog.com/doc/
  Process: 1159 ExecStart=/usr/sbin/rsyslogd -n $SYSLOGD_OPTIONS (code=exited,
status=0/SUCCESS)
 Main PID: 1159 (code=exited, status=0/SUCCESS)

May 30 11:07:50 maximus systemd[1]: Starting System Logging Service...
May 30 11:07:50 maximus systemd[1]: Started System Logging Service.
May 30 11:54:25 maximus systemd[1]: Stopping System Logging Service...
May 30 11:54:25 maximus systemd[1]: Stopped System Logging Service.
3

Fixes: 1092