virtio-net migration fix (Mark McLoughlin)

We are failing to save whether the guest will supply us rx
buffers using the new mergeable format; this can cause a
migrated guest to crash with:

   virtio-net header not in first element

Bump the savevm version number and refuse to load v1 saves
just to be on the safe side.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6221 c046a42c-6fe2-441c-8c8c-71466251a162
