Create subnet object in sync port
Create subnet object in sync port

Avoid losing port segmentation_id data in case sync port is
called before sync_router.
Create subnet object and update data on sync router

Change-Id: If5342ab8dada650e623e37080f01ca309d5463e2

FrankDuan/df_code,FrankDuan/df_code,no2key/dragonflow,openstack/dragonflow,neoareslinux/dragonflow,openstack/dragonflow,openstack/dragonflow,neoareslinux/dragonflow,FrankDuan/df_code,no2key/dragonflow