Fix loading of Monasca Grafana dashboards

This is a minimal fix to support loading dashboards into the Monasca
Grafana fork. It firstly aligns the default Monasca Grafana control
plane organisation and Monasca Grafana local admin username with Kolla
Ansible to make the feature easier to use. Secondly, it extracts the
associated OpenStack project name from this variable by stripping off
the OpenStack domain.

Longer term we may wish to move the dashboard loading functionality into
Kolla Ansible, now that it supports deploying Monasca.

Affects Rocky onwards.

Change-Id: I77c94edf654565a12ce8be681e3c9b16caa55c86
Story: 2007477
Task: 39186