Use elevated context when retrieving ports
Use elevated context when retrieving ports

External gateway ports are created as admin, hence need elevated
context for retrieval.

Change-Id: Id4d1d41efc11fe55423fa0d4e2a183edaff8e715
Closes-bug: 1508583

noironetworks/group-based-policy,jiahaoliang/group-based-policy,noironetworks/group-based-policy,jiahaoliang/group-based-policy,stackforge/group-based-policy,stackforge/group-based-policy