Replace six.iteritems() with .items()

1.As mentioned in [1], we should avoid usingg
six.iteritems to achieve iterators. We can
use dict.items instead, as it will return
iterators in PY3 as well. And dict.items/keys
will more readable. 2.In py2, the performance
about list should be negligible, see the link [2].
[1] https://wiki.openstack.org/wiki/Python3
[2] http://lists.openstack.org/pipermail/openstack-dev/2015-June/066391.html

Change-Id: I71c13040318eca6e5ed993e8aa03f8003986a71c

glanceclient/tests/unit/test_http.py

@@ -134,7 +134,7 @@ class TestClient(testtools.TestCase):
         http_client.get(path)
 
         headers = self.mock.last_request.headers
-        for k, v in six.iteritems(identity_headers):
+        for k, v in identity_headers.items():
             self.assertEqual(v, headers[k])
 
     def test_language_header_passed(self):
@@ -326,7 +326,7 @@ class TestClient(testtools.TestCase):
                         'LOG.debug called with no arguments')
 
         needles = {'key': key, 'cert': cert, 'cacert': cacert}
-        for option, value in six.iteritems(needles):
+        for option, value in needles.items():
             if value:
                 regex = ".*\s--%s\s+('%s'|%s).*" % (option, value, value)
                 self.assertThat(mock_log.call_args[0][0],

glanceclient/tests/unit/v2/test_metadefs_objects.py

@@ -13,7 +13,6 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import six
 import testtools
 
 from glanceclient.tests.unit.v2 import base
@@ -276,7 +275,7 @@ class TestObjectController(testtools.TestCase):
         obj = self.controller.get(NAMESPACE1, OBJECT1)
         self.assertEqual(OBJECT1, obj.name)
         self.assertEqual(sorted([PROPERTY1, PROPERTY2]),
-                         sorted(list(six.iterkeys(obj.properties))))
+                         sorted(list(obj.properties.keys())))
 
     def test_create_object(self):
         properties = {