ML2 Cisco Nexus MD: VXLAN Bug - Two hosts

Fix issue where two hosts configured under one Nexus switch was
causing a database access traceback on the 2nd host's port create.

Change-Id: I5a9a3e98660eaddded02bc48937d4f646d93cf6d
Merge "ML2 Cisco Nexus MD: VXLAN Bug - Two hosts" into staging