schema: Fix wrong type in GuestNetworkDeviceInfo

Changed inet and inet6 in GuestNetworkDeviceInfo to be lists as they are
actually reported by vdsm and received by the engine.

Change-Id: I003d15d55897c0d6135ceb283ca30ba3ccc078cd
Signed-off-by: Dima Kuznetsov <dkuznets@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/27263
Reviewed-by: Dan Kenigsberg <danken@redhat.com>