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.
A `case` statement here would be better style, I reckon.