replace dict.iteritems() with six.iteritems(dict)

According to https://wiki.openstack.org/wiki/Python3 dict.iteritems()
should be replaced with six.iteritems(dict).

Change-Id: Id8a87cf2ba68b37507f9238a48e8a224612a7b90
Merge "replace dict.iteritems() with six.iteritems(dict)"