migration: Read JSON VM description on incoming migration

migration: Read JSON VM description on incoming migration

One of the really nice things about the VM description format is that it goes
over the wire when live migration is happening. Unfortunately QEMU today closes
any socket once it sees VM_EOF coming, so we never give the VMDESC the chance to
actually land on the wire.

This patch makes QEMU read the description as well. This way we ensure that
anything wire tapping us in between will get the chance to also interpret the
stream.

Along the way we also fix virt tests that assume that number_bytes_sent on the
sender side is equal to number_bytes_read which was true before the VMDESC
patches and is true again with this patch.

Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Tested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>