engine: Maintain NetworkUser role id for VnicProfileUser

The role id of the NetworkUser should be preserved for
VnicProfileUser so the same resource could be reachable
via the api.

Change-Id: I2ebd6c4da455696f82fa8f53cfcb35d8c97a479f
Signed-off-by: Moti Asayag <masayag@redhat.com>