Remove unnecessary setUp function in testcase

In testcase, setUp will be called automatically. This patch used to
remove setUp functions that do nothing. Besides, it will keep code clean.

Change-Id: Id7641bc116c26f8b11f4441524c5e2c0442362a8

manila/tests/db/test_api.py

@@ -24,9 +24,6 @@ from manila import test
 class DBInterfaceTestCase(test.TestCase):
     """Test cases for the DB Interface methods."""
 
-    def setUp(self):
-        super(self.__class__, self).setUp()
-
     def test_interface_methods(self):
         """Ensure that implementation methods match interfaces.