With the external user/group management fixed, correct the unit tests.

The unit tests were incorrectly expecting the removed data back when
removing external users.

tests/test_xmlrpc/test_sudorule_plugin.py

@@ -280,7 +280,7 @@ class test_sudorule(XMLRPC_test):
         assert ret['completed'] == 1
         failed = ret['failed']
         entry = ret['result']
-        assert 'externaluser' not in entry
+        assert entry['externaluser'] == ()
 
     def test_a_sudorule_add_runasexternaluser(self):
         """
@@ -306,7 +306,7 @@ class test_sudorule(XMLRPC_test):
         assert ret['completed'] == 1
         failed = ret['failed']
         entry = ret['result']
-        assert 'ipasudorunasextuser' not in entry
+        assert entry['ipasudorunasextuser'] == ()
 
     def test_a_sudorule_add_runasexternalgroup(self):
         """
@@ -332,7 +332,7 @@ class test_sudorule(XMLRPC_test):
         assert ret['completed'] == 1
         failed = ret['failed']
         entry = ret['result']
-        assert 'ipasudorunasextgroup' not in entry
+        assert entry['ipasudorunasextgroup'] == ()
 
     def test_a_sudorule_add_option(self):
         """