Automatically configure Monasca Grafana datasource

In Kolla, an OpenStack project is created to store logs and metrics
harvested from the control plane by Monasca. This commit enables
the Monasca Datasource in the Grafana organisation which maps to
this OpenStack control plane project. What this means in practice
is that if a user logs into Monasca Grafana, and has access to the
the control plane project, they will immediately be able to create
dashboards using data from Monasca which has been gathered from the
control plane.

Support to enable creation of this datasource for other OpenStack
projects can be added in a separate commit.

Partially-Implements: blueprint monasca-grafana
Change-Id: I03e741ddb1c582b7280c64637ed3e3683df6419b