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_offline.py b/tcp_tests/tests/system/test_offline.py
index 83f3766..44b82f0 100644
--- a/tcp_tests/tests/system/test_offline.py
+++ b/tcp_tests/tests/system/test_offline.py
@@ -162,7 +162,7 @@
         LOG.info("*************** DONE **************")
 
     def test_deploy_day1(self, show_step, config, underlay, hardware,
-                         common_services_deployed, salt_deployed):
+                         core_deployed, salt_deployed):
         """Test for deploying an mcp from day01 images
 
         Scenario: