nfsnotify resource fails to start with 'unknown error' and logs show "sm-notify[<pid>]: my_name 'X.X.X.X' is unusable: Name or service not known" in a RHEL 6 or 7 High Availability cluster with pacemaker

Issue

• The nfsnotify resource I've configured won't start, and pcs status shows 'unknown error'

Failed actions:
    notify173_start_0 on rhel6-node2-pcmk.example.com 'unknown error' (1): call=167, status=complete, last-rc-change='Tue Jan 20 15:51:14 2015', queued=0ms, exec=95ms
    notify173_start_0 on rhel6-node1-pcmk.example.com 'unknown error' (1): call=239, status=complete, last-rc-change='Tue Jan 20 15:51:06 2015', queued=0ms, exec=108ms

• When I start my NFS resource group, the nfsnotify resource doesn't start and the logs show an error from sm-notify~

Jan 20 16:06:59 rhel6-node1-pcmk sm-notify[23339]: Version 1.2.3 starting
Jan 20 16:06:59 rhel6-node1-pcmk sm-notify[23339]: my_name '192.168.143.173' is unusable: Name or service not known