Use dict.items() for adding Python 3 compatibility

Replacing dict.iteritems()/.itervalues() with
six.iteritems(dict)/six.itervalues(dict) was preferred in the past,
but there was a discussion suggesting to avoid six for this.

ref:
http://lists.openstack.org/pipermail/openstack-dev/2015-June/066391.html

Partially implements: blueprint python3
Change-Id: Ie931bc02f558f6db3677b44f645eb3bdf78ccae8

kolla/cmd/build.py

@@ -488,7 +488,7 @@ class KollaWorker(object):
         if self.image_statuses_bad:
             LOG.info("Images that failed to build")
             LOG.info("===========================")
-            for name, status in six.iteritems(self.image_statuses_bad):
+            for name, status in self.image_statuses_bad.items():
                 LOG.error('%s Failed with status: %s', name, status)
 
         if self.image_statuses_unmatched:
@@ -583,7 +583,7 @@ class KollaWorker(object):
         for image in self.images:
             sort_images[image['fullname']] = image
 
-        for parent_name, parent in six.iteritems(sort_images):
+        for parent_name, parent in sort_images.items():
             for image in sort_images.values():
                 if image['parent_name'] == parent_name:
                     parent['children'].append(image)

kolla/common/config.py

@@ -240,7 +240,7 @@ def get_source_opts(type_=None, location=None, reference=None):
 
 
 def gen_all_source_opts():
-    for name, params in SOURCES.iteritems():
+    for name, params in SOURCES.items():
         type_ = params['type']
         location = params['location']
         reference = params.get('reference')