Add a new objectclass, ipaObject, that will add a UUID to many IPA objects

ipaObject is defined as an auxiliary objectclass so it is up to the
plugin author to ensure that the objectclass is included an a UUID generated.
ipaUniqueId is a MUST attribute so if you include the objectclass you must
ensure that the uuid is generated.

This also fixes up some unrelated unit test failures.

tests/test_xmlrpc/test_host_plugin.py

@@ -45,6 +45,7 @@ class test_host(XMLRPC_test):
         assert_attr_equal(res, 'description', self.description)
         assert_attr_equal(res, 'fqdn', self.fqdn)
         assert_attr_equal(res, 'localityname', self.localityname)
+        assert_attr_equal(res, 'objectclass', 'ipaobject')
 
     def test_2_host_show(self):
         """