Handle the following sequence of events correctly in Agent UVE code
--VM Disassociation from VMI
--VM Deletion
--VM Addition
--VM Reassociation to same VMI
(Because VM gets deleted and re-added, store VM UUID instead of VM pointer as metadata on interface entry)
Change-Id: If7a2030655ac99e0f7b9ba75b3a56a53ae5d779b