engine: Update nics with user configuration

There is a need to persist the data configured by
the user on the interfaces. Since some of the devices
are created after being reported by VDSM, there is
a need to make sure the user date is persisted.

Change-Id: Ibcb860cf638286c469ea032ffd0fa4291214bf77
Signed-off-by: Moti Asayag <masayag@redhat.com>