Comment # 5 on bug 960118 from Roger Zhou

Further more testing, the problem scenario is true when the redundant link of
DC is down, and then the other node couldn't re-join back. That said, there are
chance to put this two-node cluster under risk, and this bug need be fixed.

The frequency to reproduce this problem is different for the different
operation.

Reproduce Approach 1, 50% chance, by 
# systemctl stop pacemaker
# systemctl start pacemaker

Reproduce Approach 2, <20% chance, by 
# reboot

Reproduce Approach 3, <10 chance, by 
# systemctl restart pacemaker