Changes to enable network_cli and netconf on iosxr integration tests. (#35269)

* * Changes to enable network_cli and netconf on modules.
* limits connection local for single TC per playbook.

* * adds a note on why only 1 TC is executed with connection: local

lib/ansible/module_utils/network/iosxr/iosxr.py

@@ -359,6 +359,8 @@ def get_oper(module, filter=None):
 
     if filter is not None:
         response = conn.get(filter)
+    else:
+        return None
 
     return to_bytes(etree.tostring(response), errors='surrogate_then_replace').strip()