Functional test for Multiple Gateways source routing

adding assertions on the source routing definitions that are configured
when the network is configured with DHCP.

Change-Id: Ib510bb56c205dffc98aa2bae3f55c1b4c7f6f56f
Signed-off-by: ibarkan <ibarkan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/33612
Reviewed-by: Assaf Muller <amuller@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>