engine: VnicProfile info isn't restored on snapshot preview

The vnic profile information wasn't updated when a snapshot
of a VM was preview. Since the snapshot uses the OVF writer
and reader, the vnic profile id isn't kept with the network
name and the profile name. These should be resolved before
adding the interface to the system.

Change-Id: If9880b957bdccc1dae0364919c3958479eabbc30
Bug-Url: https://bugzilla.redhat.com/998634
Signed-off-by: Moti Asayag <masayag@redhat.com>