Increase unit test coverage for system agent
Increase unit test coverage for system agent

Implements bp: murano-unit-test-coverage
Co-Authored-By: Felipe Monteiro <felipe.monteiro@att.com>
Co-Authored-By: David Purcell <david.purcell@att.com>
Co-Authored-By: Julian Sy <julian.sy@att.com>

Change-Id: Iba421cc329f214537ea9205b954fadb9df5b94a2

openstack/murano,openstack/murano