[exim] ACL time content scanning failover

Greetings all...

We are trying to failover clamav scanning to a 2nd server in case the
1st server is down, or not functioning properly.

Exim doc gives us an example on how to scan the the message twice using
two different AV scanners.

But I couldn't figure out a way of using the 2nd scanner just in case
the 1st one fails.

Any hints?

Thanks :)