Add docstrings to system tests

Change-Id: I239f903707a560b09164289cd6225fc35dc5a6bc

	modified:   tests/base_test_case.py
	modified:   tests/test_admin_node.py
	modified:   tests/test_ceph.py
	modified:   tests/test_ha.py
	modified:   tests/test_neutron.py
	modified:   tests/test_services.py