Update X_service_check.py plugins

This commit updates the X_service_check.py plugins to accept filtering
agent/service lists by host.  This means that we can run the plugin
multiple times per ansible hosts group and only write the necessary
metrics for that specific hosts group.

We also generalise the metric name to not include host/container name
which makes creating alarms slightly more straight-forward.

The downside to this approach is that we will end up running this
plugin a good bit more frequently, which means more nova-api hits.