Why is a pacemaker cluster node fenced when stopped when maintenance-mode is enabled on RHEL 6?

Issue

• Why is a pacemaker cluster node fenced when stopped when maintenance-mode is enabled on RHEL 6?
• A pacemaker cluster node was fenced when the cluster node was stopped with service pacemaker stop when maintenance-mode is enabled on RHEL 6. There was errors when pacemaker was stopped.

# service pacemaker stop
Waiting for shutdown of managed resources                  [  OK  ]
DLM lockspace still in use
Deactivating clustered VG(s):   Logical volume vg_shared_1/lvol1 contains a filesystem in use.
  Can't deactivate volume group "vg_shared_1" with 1 open logical volume(s)
                                                           [FAILED]
Leaving fence domainfound gfs2 file system mounted from /dev/dm-2 on /mnt/vg_shared_1-lvol1
found dlm lockspace /sys/kernel/dlm/clvmd
found dlm lockspace /sys/kernel/dlm/gfs2-1
fence_tool: cannot leave due to active systems
Signaling Pacemaker Cluster Manager to terminate           [FAILED]
Waiting for cluster services to unload                     [  OK  ]
Stopping cluster:
   Leaving fence domain...                                 [  OK  ]
   Stopping gfs_controld..............

• A pacemaker cluster node was fenced when the cluster node was stopped with service pacemaker stop --skip-cman when maintenance-mode is enabled on RHEL 6. There was errors when pacemaker was stopped.

# service pacemaker stop 
Waiting for shutdown of managed resources                  [  OK  ]
DLM lockspace still in use
Deactivating clustered VG(s):   Logical volume vg_shared_1/lvol1 contains a filesystem in use.
  Can't deactivate volume group "vg_shared_1" with 1 open logical volume(s)
                                                           [FAILED]
Leaving fence domain found gfs2 file system mounted from /dev/dm-2 on /mnt/vg_shared_1-lvol1
found dlm lockspace /sys/kernel/dlm/clvmd
found dlm lockspace /sys/kernel/dlm/gfs2-1
fence_tool: cannot leave due to active systems
Pacemaker Cluster Manager is already stopped               [  OK  ]