Modify service_test.py::ServiceTest::test_resolve_env to reflect new behavior

Signed-off-by: jrabbit <[email protected]>

tests/integration/service_test.py

@@ -860,7 +860,6 @@ class ServiceTest(DockerClientTestCase):
             'FILE_DEF': 'F1',
             'FILE_DEF_EMPTY': '',
             'ENV_DEF': 'E3',
-            'NO_DEF': ''
         }.items():
             self.assertEqual(env[k], v)