Heat driver config description updates
Heat driver config description updates

It updates the description for interval to mention about the
metric is in seconds.

Change-Id: Ia7f9b870083e83f19de1218fcca600da98de5946

zeinsteinz/tacker,openstack/tacker,stackforge/tacker,stackforge/tacker,openstack/tacker,zeinsteinz/tacker,openstack/tacker