[Twisted-Python] buildbot is back

[Glyph]

When migrating it to a new VM, we seem to have somewhat underprovisioned buildbot.twistedmatrix.com.  I've just moved it from a 1G to a 2G instance.  Sorry about the downtime!  Hopefully this is enough RAM for it to do its job.  It seemed to happily consume only a few hundred megs when we were doing test builds, but there's some kind of load spike that happens periodically which was OOM killing it and I believe this change should fix it.

-glyph