Use the more common os_ names for novaclient

Users are quite accustomed to using these names, so we'll use
them. Also we may eventually want to monitor more than just
Nova.

The old parameters are not kept and will not be utilized anymore.

Change-Id: I17b6cb765ce73478204a66ae7fa79f4fb0cda14c
Refactor nagios3 element to refresh more often

Previously the element would only refresh from Nova when the
Heat configuration was changed. But we want it to refresh
whenever nova changes.

Note that we won't actually remove hosts that go away.

Change-Id: Ic8af7f30ccc0cc2c64643081a6e300a354d8ad35
Merge "Use the more common os_ names for novaclient"
Merge "Refactor nagios3 element to refresh more often"