Fix neptune-mutual snapshot validation

[agostbiro]

There are currently workarounds in the snapshot validation for the openzeppelin and neptune-mutual scenarios as comparing failing RPC call indices for these two scenarios is unreliable. We think this is related to block timestamp timing issues.

Depends on: #286

Definition of Done

Use snapshot validation by comparing failing RPC call indices for the openzeppelin and neptune-mutual scenarios.

EDIT: openzeppelin has been fixed at least since #416