Update iteritems test case to actually test iteritems.
Update iteritems test case to actually test iteritems.

This patch updates the jsonutils.to_primitive() test case for when an
object has an iteritems() method.  The previous implementation was
mostly a copy of another test and didn't actually test calling
iteritems() at all.  Now it does.

This is used by NovaBase in nova.db.sqlalchemy.models.

Related to nova blueprint no-db-messaging.

Change-Id: Ie1d71b859219392ab35b82dd3c7932b30e759c89

openstack/oslo.serialization,varunarya10/oslo.serialization,cybertron/oslo.serialization