* transfer: reply with refused

When the *transfer* plugin is not loaded and of the handlers will still
see the AXFR/IXFR request because it is not intercepted.

They need to reply with REFUSED in that case. Update file, auto and k8s
to do this. Add testcase in the file plugin.

Ideally *erratic* should be moved over as well, but maybe that's
*erratic*

This is a bug fix.
Signed-off-by: Miek Gieben <miek@miek.nl>

* import path
Signed-off-by: Miek Gieben <miek@miek.nl>