Rename core fixtures to match the drivetrain component names

The following changes:
  common_services_deployed -> core_deployed
  sl_deployed -> stacklight_deployed

Change-Id: I6e505d2ef96053b19b2d43b0214f5a30f71ae8ea
diff --git a/tcp_tests/tests/system/test_oss_install.py b/tcp_tests/tests/system/test_oss_install.py
index f62f1c8..15bdf3e 100644
--- a/tcp_tests/tests/system/test_oss_install.py
+++ b/tcp_tests/tests/system/test_oss_install.py
@@ -26,7 +26,7 @@
     @pytest.mark.fail_snapshot
     def test_oss_install_default(self, underlay, show_step,
                                  oss_deployed, openstack_deployed,
-                                 sl_deployed):
+                                 stacklight_deployed):
         """Test for deploying an OSS environment and check it
 
         Scenario: