engine: Include network QoS in Setup Networks

Modified the Setup Networks VDS command cycle to also account for QoS
configuration on the host's networks - any QoS configuration attached
to a network is serialized in the Setup Networks command, and any QoS
configuration reported when the network data is collected back from
VDSM is deserialized into VdsNetworkInterface and persisted.

Change-Id: I5f0d2c3fe430961f7a402518ce1358938ed52063
Signed-off-by: Lior Vernia <lvernia@redhat.com>