No, really record when a job finished.

(The os module isn't available from Redis' Lua environment.)
Fix assorted Redis-in-Lua script stupidities.

In particular:

- there's no argcount required when running scripts
- hey, I don't have table_show.lua here
Make finished_at an integral UNIX timestamp.

(Actually, that's a lie.  We're going to get strings, but they'll be
strings that can be coerced to integers.)
Bump pipeline version.

(The abort/log script change is big enough to warrant this.)