engine: Change AttachNetworkToVdsGroupCommand to non-transactive

The command will be used also for configuring the
network on the hostis. For that purpose the class
 should be managed as a non-transactive.

Change-Id: I673024917d5308bfdfd2030eb9a2479f7e37ee03
Signed-off-by: Moti Asayag <masayag@redhat.com>