The same jobs run multiple times when the server runs on 2.1.1

[joakimk]

I noticed this behavior after we upgraded an app to ruby 2.1.1 and started running the testbot server on that as well.

This also caused a secondary problem where the runner ran different jobs using the same TEST_ENV_NUMBER causing deadlocks :).

For now we've opted to running the server on 1.9.3 and the runners on 2.1.1.