The "delay" option was a hack that was introduced to allow writing "nodelay".
We are adding a "nodelay" option to be used as "nodelay=on", so recommend it
instead of "delay".

This is quite ugly, but a proper deprecation of "delay"
cannot be done if QEMU starts suggesting it.  Since it's the
only case I opted for this very much ad-hoc patch.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>