Update the undo operation so they return a success/error code rather than taking out parameter

Summary:
This is backport from core. It makes the API much more understandable. See https://github.com/bitcoin/bitcoin/pull/10297/commits/db994b2de93f52c9e7bed8529ca925de5064a46f for details.

I would rather return some object that forces you to check, but we have this and it is needed for the utxo work, so be it.

Test Plan:

make check
../qa/pull-tester/rpc-tests.py -extended

Reviewers: freetrader, #bitcoin_abc

Reviewed By: freetrader, #bitcoin_abc

Subscribers: CCulianu

Differential Revision: https://reviews.bitcoinabc.org/D364