change cucumber redis ttl shim, various test fixes

The change to the Lua script was necessary to make the new scenario work (the notification blocks were being incorrectly expired before), and that exposed a few edge-casey notification rules tests which needed to have their times altered. Most of this may seem pretty simple, but I'd appreciate some review as it's mucking with a complex area of the code.
No, I don't have a test for this -- the new scenario passes because the previous Lua script had inconsistent behaviour with multiple time jumps. We should probably test for this, it seemed to be needed for me for rollup to cease correctly when the alerting checks go back under the threshold.