Adding Nagios Support

This commit adds an option to install Nagios to monitor the
openstack components. Initially we are only monitoring a small
subset of what could eventually be monitored
http://bugzilla.redhat.com/show_bug.cgi?id=912768

Change-Id: I176876e5ecc35e7c58ef49534341939fd7998701
Merge "Adding Nagios Support"