Re-enabling upgrade test

Author: Nelson Wang

tests/test_docker_splunk.py

@@ -1219,7 +1219,6 @@ def test_adhoc_1so_web_ssl(self):
             except OSError:
                 pass
 
-    @pytest.mark.skip(reason="Ask Nelson")
     def test_adhoc_1so_upgrade(self):
         # Pull the old image
         for line in self.client.pull("splunk/splunk:{}".format(OLD_SPLUNK_VERSION), stream=True, decode=True):