packaging: spec: all-in-one: do not allow disabling NetworkManager

because of various reasons, vdsm requires disabling NetworkManager,
however in all-in-one configuration, it may do much more harm than good.

so for all-in-one configuration we leave NetworkManager up, under the
assumption that there won't be significant network changes via the
engine->vdsm communication.

Change-Id: I6be399e070ede11a10f0f7636d71acc45b942872
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>