whoami.py: Type error when running tests

While test run the TypeError occured in whoami.validate_output().
There should be 'tuple' type in output too.

Fixes: https://pagure.io/freeipa/issue/7050
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

ipaserver/plugins/whoami.py

@@ -87,7 +87,8 @@ class whoami(Command):
     has_output = (
         output.Output('object', unicode, _('Object class name')),
         output.Output('command', unicode, _('Function to get details')),
-        output.Output('arguments', list, _('Arguments to details function')),
+        output.Output('arguments', (list, tuple),
+                      _('Arguments to details function')),
     )
 
     def execute(self, **options):