vl.c: Do not set 'type' property in obj_set_property()

Filter out also 'type' property when setting
object's properties.

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>