Description of problem:
I have a corosync with existing but empty /etc/corosync/corosync.conf (which
happened unintentionally). Starting corosync using "systemctl start corosync"
gives you no error output -- it only says that it has failed [1]. Looking into
/var/log/messages [2] gives you the same non-specific information about why the
failure happened. To find the real problem you must run corosync on commandline
with -f to see that some error message [3]. 

I believe that error output should be visible in /var/log/messages


Version-Release number of selected component (if applicable):
corosync-2.3.0-3.el7.x86_64

How reproducible: always

Steps to Reproduce:
1. have empty /etc/corosync/corosync.conf
2. run "systemctl start corosync"

Actual results: no error messages 

Expected results: error message in /var/log/messages

Additional info:

[1]
# systemctl status corosync
corosync.service - Corosync Cluster Engine
   Loaded: loaded (/usr/lib/systemd/system/corosync.service; enabled)
   Active: failed (Result: exit-code) since Mon 2013-05-27 08:21:13 EDT

May 27 08:21:02 virt-062 systemd[1]: Starting Corosync Cluster Engine...
May 27 08:21:13 virt-062 corosync[958]: [62B blob data]
May 27 08:21:13 virt-062 systemd[1]: corosync.service: control process exited, code=exited status=1
May 27 08:21:13 virt-062 systemd[1]: Failed to start Corosync Cluster Engine.
May 27 08:21:13 virt-062 systemd[1]: MESSAGE=Unit corosync.service entered failed state.

[2]
# grep corosync /var/log/messages
...
May 27 05:34:04 virt-062 corosync[1602]: Starting Corosync Cluster Engine (corosync): [FAILED]#015[  OK  ]
May 27 05:34:04 virt-062 systemd[1]: corosync.service: control process exited, code=exited status=1
May 27 05:34:04 virt-062 systemd[1]: MESSAGE=Unit corosync.service entered failed state.11

[3]
# corosync -f 
notice  [MAIN  ] Corosync Cluster Engine ('2.3.0'): started and ready to provide service.
info    [MAIN  ] Corosync built-in features: dbus rdma systemd xmlconf snmp pie relro bindnow
error   [MAIN  ] Could not open /etc/corosync/authkey: No such file or directory
error   [MAIN  ] Corosync Cluster Engine exiting with status 8 at main.c:1166.