CI: Add monasca scenario

Adds the following new Zuul job for testing deployment of Monasca and
associated services:

* kolla-ansible-centos8-source-monasca

All core OpenStack services except for Keystone are disabled to ensure
enough memory is available.

A follow up patch will replace the basic tests here with Tempest.

Co-Authored-By: Doug Szumski <doug@stackhpc.com>

Change-Id: I5d33fd3d7b69798ba0aa23509f7b809065f61c19

zuul.d/base.yaml

@@ -148,6 +148,17 @@
     vars:
       scenario: masakari
 
+- job:
+    name: kolla-ansible-monasca-base
+    parent: kolla-ansible-base
+    voting: false
+    files:
+      - ^ansible/roles/(elasticsearch|influxdb|kafka|kibana|monasca|storm|zookeeper)/
+      - ^tests/test-monasca.sh
+      - ^tests/test-dashboard.sh
+    vars:
+      scenario: monasca
+
 - job:
     name: kolla-ansible-mariadb-base
     parent: kolla-ansible-base