Confirm "Exhaustion" condition is necessary

[pipermerriam]

See: https://github.com/ethereum/py-wasm/pull/87/files/1d9464d11bff55e06816e9c43ab5ed10f42510b9#r262251679

That condition has been in the code since the legacy implementation. We need to re-evaluate whether it is 1) needed and 2) what the right value is for the limit if it is needed.