Isolate IETF models in OpenConfig to own bundle

Change-Id: I15fff358582dd7b361d015c2d30c981a703fd1be
diff --git a/modules.defs b/modules.defs
index bd785ba..37cb04b 100644
--- a/modules.defs
+++ b/modules.defs
@@ -261,6 +261,7 @@
 ]
 
 MODELS = [
+    '//models/ietf:onos-models-ietf-oar',
     '//models/common:onos-models-common-oar',
     '//models/huawei:onos-models-huawei-oar',
     '//models/openconfig:onos-models-openconfig-oar',