TLS iochannel will inherit io_shutdown() from the master ioc, however we
missed to do that on the server side.

This will e.g. allow qemu_file_shutdown() to work on dest QEMU too for
migration.

Acked-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>