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: I10ae120a9af5e79a2d9ddb7d2c94dda128e11ea4
Signed-off-by: Moti Asayag <masayag@redhat.com>