core: Change Network QoS units in the VmInfoBuilder

Since engine is using Mb and vdsm uses Kb for Network QoS, the values in
the VmInfoBuilder should have been multiplied by 1024.

Change-Id: Ieb78b8eeb8e5ae0a7c964773a4eb8fa98da4d3a5
Signed-off-by: Ofri Masad <omasad@redhat.com>