Cleans up the logs in the L2 genesis generation script.
Very small fix just to clean things up. Also moves to
using `prank` of `start/stop` `prank` to catch hanging
calls to `prank` as if a prank is active you cannot call
`prank` but you can call `startPrank`. This ensures that
we know if a prank is active or not instead of one being
silently active.