Revert !2434 (with commentary)

Closes #1401 (closed) by reverting !2434 (merged) (adding comments as to why).

This was based on a talk about current options.
Note that for #1374 (closed) the cycling item is skipped with a return nil, nil without waiting one minute (the keysign timeout period) or ending the processTransactions list, so similarly invalid items could not be used to deliberately jam a chain's outbounds.