The ceilometer setup script is a setup script not a test so it should not raise a skip exception if it is not needed. The fact that it does is my fault and was implemented on my recommendation.
Porting the Amulet tests from Ceilometer to the Zaza framework. The Amulet tests can be found here: https://opendev.org/openstack/charm-ceilometer/src/branch/master/tests/basic_deployment.py