engine: vNic name is overridden by VM name

A bug was caused by refactor code which changed the
setter of the nic's vm name and used the nic's name setter
instead.

Change-Id: I211cefbe896d93ae7500f480d63a26d49ea7541e
Bug-Url: https://bugzilla.redhat.com/916620
Signed-off-by: Moti Asayag <masayag@redhat.com>