tests: fix qvm-appmenus get-available unit test domain input

Author: Jayant-kernel

qubesappmenus/tests.py

@@ -742,7 +742,7 @@ def test_132_get_available_does_not_require_unstable_flag(
 
         parse_args.return_value = types.SimpleNamespace(
             all_domains=False,
-            domains=[vm],
+            domains=[vm.name],
             remove=False,
             init=False,
             get_whitelist=False,