The ceph_health check in Nagios incorrectly sets the warning and
error level to 0. The ceph_health_status metric's value of 0
indicates the cluster is healthy, while 1 indicates a warning and
2 indicates an error state. The Nagios check for ceph_health is
updated to reflect these values
Change-Id: Iffe80f1c34f6edee6370dd7e707e5f55f83f1ec1