(SERVER-150) flush jruby instances

I don't have a huge problem with that patch, but, it adds an extra argument to quite a few function signatures.  If, in the future, there is any other state that we need for that agent to maintain, we would have to keep adding more and more arguments to all of those function signatures.

My preference would be to not tackle this right now and perhaps bring it up as a discussion topic at some point in the future, but if I'm outvoted on this then we can try to address it now.  @camlow325 any thoughts?