Fix wrong code duplication in utils.itersubclasses()

Change-Id: Ic34be7cb10b5aba723394e06ddff69cb09fe698d
Signed-off-by: Zhi Yan Liu <zhiyanl@cn.ibm.com>

osprofiler/_utils.py

@@ -105,7 +105,6 @@ def itersubclasses(cls, _seen=None):
         subs = cls.__subclasses__()
     except TypeError:   # fails only when cls is type
         subs = cls.__subclasses__(cls)
-    subs = cls.__subclasses__()
     for sub in subs:
         if sub not in _seen:
             _seen.add(sub)

tests/test_utils.py

@@ -92,3 +92,8 @@ class UtilsTestCase(test.TestCase):
             pass
 
         self.assertEqual([B, C, D], list(utils.itersubclasses(A)))
+
+        class E(type):
+            pass
+
+        self.assertEqual([], list(utils.itersubclasses(E)))