Test compatibility mode on Versi

[Sophia-Gold]

In order to merge asynchronous backing to master we need more confidence it works in compatibility mode. We should run a significant number of nodes (40+) on Versi, half on master and half on the async backing branch, and leave it up for a good amount of time (maybe over a weekend so as not to block development) to observe the behavior. This can wait until after SRLabs has returned their initial audit findings.