exportfs resource fails to stop with "Failed to un-export file system" in a RHEL 7 High Availability cluster serving HA-NFS exports

Issue

• Our node is getting fenced after failing to stop an exportfs resource.
• exportfs is reporting "Failed to un-export file system" when we move the service around the cluster

exportfs(export_projects-9)[33713]: 2016/04/21_16:52:01 INFO: Un-exporting file system ...
exportfs(export_projects-9)[33713]: 2016/04/21_16:52:01 ERROR: unexporting 10.1.1.1:/path/to/export
exportfs(export_projects-9)[33713]: 2016/04/21_16:52:01 INFO: Unlocked NFS export /path/to/export
exportfs(export_projects-9)[33713]: 2016/04/21_16:52:01 ERROR: Failed to un-export file system
Apr 21 16:52:01 [4745] node1.example.com       lrmd:   notice: operation_finished:   example_export_stop_0:33713:stderr [ ocf-exit-reason:Failed to un-export file system ]
Apr 21 16:52:01 [4745] node1.example.com       lrmd:     info: log_finished: finished - rsc:eexample_export action:stop call_id:215 pid:33713 exit-code:1 exec-time:104ms queue-time:0ms
Apr 21 16:52:01 [4748] node1.example.com       crmd:   notice: process_lrm_event:    Operation example_export_stop_0: unknown error (node=node1.example.com, call=215, rc=1, cib-update=17        9, confirmed=true)
Apr 21 16:52:01 [4748] node1.example.com       crmd:   notice: process_lrm_event:    node1.example.com-example_export_stop_0:215 [ ocf-exit-reason:Failed to un-export file system\n ]