[Xmlhttprequest] Fix xmlhttprequest tests.

Tests are incompatible with the XMLHTTPRequest
spec: http://www.w3.org/TR/XMLHttpRequest/
In current implementation send() may be called after abort()
This causes tests to fail.

Change-Id: I09720b8a2c88b277cf846f584b0ccf1002aeff6a
Merge pull request #556 from tiwanek/XWALK-2205

[Xmlhttprequest] Fix xmlhttprequest tests - abort-upload-event-*