Make compute support monitors and store metrics

According to the 'nova.conf', compute can call the
appropriate monitors and store metrics into compute nodes
as a json dictionary.

This is part of the blueprint utilization-aware-scheduling and
the blueprint generic-host-state-for-scheduler.

Change-Id: I2d9bde7ae838f2588c19874d87de6653859b3ac4
Merge "Make compute support monitors and store metrics"