This adds a basic check for capacity utilization for persistent
volume claims. To accomplish this, it adds a basic alerting rule
to prometheus that triggers after a persistent volume's usage
exceeds 80%, and triggers 5 minutes after that state has been
reached. In addition, there is a service check added to the
nagios chart that will query Prometheus to check if the alarm
for that threshhold is firing for any of the volume claims.
Change-Id: I862c860ac479a715733202f679bb151885d7aa7c
561780f347