Recover a destination when it stops failing

In #28897 (moved) we count consecutive destination failures. We stop a destination when it fails x (=10?) consecutive times. We stop the scanners if all destinations are stopped.

As teor commented, this can be improved to:

• recover a destination if it starts working again after short time
• error when all destinations fail for long time
• let the operator configure the time or number of failures to consider a destination is failing.

Implementation possibilities:

• A destination failing can be tried again with a low probability
• Wait for some minutes before considering a destination fails (after it has failed)