Extend setupNetworks API to accept defaultRoute

Previously defaultRoute was True for the management network,
now it is received from the client. For backwards compatability,
if defaultRoute is not received from the client, it is set
if the network being configured is the management network.

Change-Id: I9b2ff711155eb0bd79ab84e979eb82c846362374
Bug-Url: https://bugzilla.redhat.com/1015009
Signed-off-by: Assaf Muller <amuller@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/22720
Reviewed-by: Antoni Segura Puimedon <asegurap@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>