pacemaker service fails to start and/or nodes are unable to join the cluster while logs show no errors or output from pacemaker daemons in a RHEL 6 Update 7 High Availability cluster

Issue

• I updated to RHEL 6.7 and tried to restart my cluster, but pacemaker fails to start. There is nothing logged by any of the pacemaker daemons when this happens.
• Newly installed cluster nodes fails to join the cluster and pacemaker service will fail to start manually.
• pacemaker won't start after I updated it to the release from RHEL 6 Update 7
• I updated the packages on my nodes and now my nodes can't join the cluster together
• Two nodes do not join each other to form the cluster and manually starting pacemaker service fails.

# service pacemaker start
Starting cluster:
   Checking if cluster has been disabled at boot...        [  OK  ]
   Checking Network Manager...                             [  OK  ]
   Global setup...                                         [  OK  ]
   Loading kernel modules...                               [  OK  ]
   Mounting configfs...                                    [  OK  ]
   Starting cman...                                        [  OK  ]
   Waiting for quorum...                                   [  OK  ]
   Starting fenced...                                      [  OK  ]
   Starting dlm_controld...                                [  OK  ]
   Tuning DLM kernel config...                             [  OK  ]
   Starting gfs_controld...                                [  OK  ]
   Unfencing self...                                       [  OK  ]
   Joining fence domain...                                 [  OK  ]
Starting Pacemaker Cluster Manager                         [FAILED]  

# pcs cluster start
Starting Cluster...
Starting Pacemaker Cluster Manager                         [FAILED]

Error: unable to start pacemaker