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_ipsec_nat.py

@@ -38,6 +38,14 @@ class IPSecNATTestCase(TemplateIpsec):
     icmp_id_in = 6305
     icmp_id_out = 6305
 
+    @classmethod
+    def setUpClass(cls):
+        super(IPSecNATTestCase, cls).setUpClass()
+
+    @classmethod
+    def tearDownClass(cls):
+        super(IPSecNATTestCase, cls).tearDownClass()
+
     def setUp(self):
         super(IPSecNATTestCase, self).setUp()
         self.tun_if = self.pg0