Call abort() from loadstart instead of readystatechange (broken test)

[The spec for abort()](http://xhr.spec.whatwg.org/#the-abort()-method) will only run the request error steps for a state of Opened if the send flag is set.

In this test, when `onreadystatechange` is fired for `readystate == 1`, the send flag hasn't yet been set (it's currently in the midst of `open()`, not `send()`, so the test will time out since it never reaches `onabort`.