[1.5.x] Fixed #19903 -- Fixed unbalanced setUp/tearDown calls in LiveServerAddress test

Backport of 6d52bcbb7c from master.

tests/regressiontests/servers/tests.py

@@ -96,6 +96,8 @@ class LiveServerAddress(LiveServerBase):
             raise Exception("The line above should have raised an exception")
         except exception:
             pass
+        finally:
+            super(LiveServerAddress, cls).tearDownClass()
 
     def test_test_test(self):
         # Intentionally empty method so that the test is picked up by the