tests/pam: Call parent class tearDown class method

Tests were passing but we were also hanging in some platforms (as debian
and ubuntu) because the resources were not released.

So fix this by ensuring that we call the parent class tearDown function
when required

tests/pam/test_pam_fprintd.py

@@ -72,6 +72,8 @@ class TestPamFprintd(dbusmock.DBusTestCase):
         # Remove pam wrapper files, as they may break other tests
         [shutil.rmtree(i) for i in glob.glob('/tmp/pam.[0-9A-z]')]
 
+        dbusmock.DBusTestCase.tearDownClass()
+
     def setUp(self):
         (self.p_mock, self.obj_fprintd_manager) = self.spawn_server_template(
             self.template_name, {})