Replace 'assertEqual(None, ...)' with 'assertIsNone(...)'

[H203] Use assertIs(Not)None to check for None (off by default) Unit
test assertions tend to give better messages for more specific
assertions. As a result, assertIsNone(...) is preferred over
assertEqual(None, ...) and assertIs(None, ...), and assertIsNotNone(...)
is preferred over assertNotEqual(None, ...) and assertIsNot(None,
...). Off by default.

TrivialFix

Change-Id: Ib635a7f73c9ab86ca6ca322542b19e7889486070

manila/tests/share/drivers/container/test_container_helper.py

@@ -107,4 +107,4 @@ class DockerExecHelperTestCase(test.TestCase):
 
         result = self.DockerExecHelper._inner_execute("fake_command")
 
-        self.assertEqual(result, None)
+        self.assertIsNone(result)

manila/tests/share/drivers/zfssa/test_zfssashare.py

@@ -506,7 +506,7 @@ class ZFSSAShareDriverTestCase(test.TestCase):
 
         ret = self._driver._verify_share_to_manage('sharename', {})
 
-        self.assertEqual(ret, None)
+        self.assertIsNone(ret)
         # Change it back to strict
         self.configuration.zfssa_manage_policy = 'strict'