Rename `taskForQuery` to `createTaskForQuery` since it always returns a task with a +1 retain count?

Normally, I would suggest changing each implementation to return an autoreleased task, but I'm scared of autoreleased tasks.

A while back, @yiding was debugging some issue where tasks would appear to hang.  He fixed it by explicitly releasing tasks when we were done with them.  (Maybe he can explain it better)

Here was his commit --
https://github.com/facebook/xctool/commit/592c01ec76ecf8df9356cbf00229a50f569cedcc