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>

API.txt

@@ -6477,7 +6477,7 @@ output: PrimaryKey('value')
 command: whoami/1
 args: 0,1,3
 option: Str('version?')
-output: Output('arguments', type=[<type 'list'>])
+output: Output('arguments', type=[<type 'list'>, <type 'tuple'>])
 output: Output('command', type=[<type 'unicode'>])
 output: Output('object', type=[<type 'unicode'>])
 default: aci/1

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):