Add red_client_seamless_migration_done_for_channel()
Add red_client_seamless_migration_done_for_channel()

This is a public RedClient API that handles updating itself rather than
having the RedChannelClient poke around at the internal structure in
rec_channel_client_seamless_migration_done().

fgouget/spice,fgouget/spice,fgouget/spice,fgouget/spice