Merge #11422: qa: Verify DBWrapper iterators are taking snapshots
bb8376b Verify DBWrapper iterators are taking snapshots (Matt Corallo)
Pull request description:
The LevelDB docs seem to indicate that an iterator will not take snapshots (even providing instructions on how to do so yourself). In several of the places we use them, we assume snapshots to have been taken. In order to make sure LevelDB doesn't change out from under us (and to prevent the next person who reads the docs from having the same fright I did), verify that snapshots are taken in our tests.
Backport of Core PR11422
Reviewers: deadalnix, Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc
Reviewed By: Fabien, jasonbcox, O1 Bitcoin ABC, #bitcoin_abc
Differential Revision: https://reviews.bitcoinabc.org/D3858