Fix yaml loading in tests (#2698) (#2702)

Co-authored-by: Konstantinos Tsakalozos <kos.tsakalozos@canonical.com>

tests/utils.py

@@ -79,7 +79,7 @@ def kubectl_get(target, timeout_insec=300):
     """
     cmd = 'get -o yaml ' + target
     output = kubectl(cmd, timeout_insec)
-    return yaml.load(output)
+    return yaml.safe_load(output)
 
 
 def wait_for_pod_state(