Assuming both Prometheus and Grafana are enabled, this change
configures Grafana such that it can use data collected by the
Prometheus server.
Partially-Implements: blueprint prometheus
Change-Id: I0290806d0c622b1de33cf7047f099795b4c780b9
grafana_ini file used in test condition doesn't exists,
use grafana_conf file instead.
Change-Id: Id5dca94aed98b0d6cf6c4f841e7380f8b8154416
Closes-Bug: #1673932