Add testing monitoring system with push acceptor Pushgateway and metric
analyzer Grafana in conjunction with nova instance. This test case is to
check how nova instance could communicate with a monitoring system, not
only for testing monitoring availability. Suchwise Openstack platform
using is justified.
However, if the issue is to check availability of monitoring system,
push_metric_locally scenario allows to push random metric locally to
Pushgateway and just check it in Grafana.
Change-Id: I00e85189b5f54c3e6fd18fa52afe7db0eda88fed
48f895b645