Fix Statecheck Race

We've observed some cases while running the state checks where we get the error Did not find pool in Midgard (Exists in Thornode). Intuitively it seems this is likely a race due to the pool_events table not guaranteed to be up to date with the latest height in block_log. This change simply compares at one block previous to the last height recorded in block_log, which anecdotally seems to resolve the race in our observation.

If my assumption above is correct, is it safe to assume that the pool_events table will never lag the latest height in block_log by more than one block?