Tests Cleanup: Fix missing calls to setUpClass/tearDownClass.

Continuation/Part 2 of https://gerrit.fd.io/r/#/c/17092/

Change-Id: Id0122d84eaf2c05d29e5be63a594d5e528ee7c9a
Signed-off-by: Paul Vinciguerra <pvinci@vinciconsulting.com>

test/test_srv6.py

@@ -24,8 +24,12 @@ class TestSRv6(VppTestCase):
     """ SRv6 Test Case """
 
     @classmethod
-    def setUpClass(self):
-        super(TestSRv6, self).setUpClass()
+    def setUpClass(cls):
+        super(TestSRv6, cls).setUpClass()
+
+    @classmethod
+    def tearDownClass(cls):
+        super(TestSRv6, cls).tearDownClass()
 
     def setUp(self):
         """ Perform test setup before each test case.