Fix broken ArcanistPhpunitTestResultParser
The ArcanistPhpunitTestResultParser has been changed
to use phutil_json_decode instead of json_decode in
That has broken the functionality as json_decode has returned
an object before but phutil_json_decode does return an array.
The code has now been adopted to work with the array result
instead of an object.
Test Plan: Run a phpunit test case
Reviewers: Blessed Reviewers, epriestley
Reviewed By: Blessed Reviewers, epriestley
Subscribers: aurelijus, epriestley
Differential Revision: https://secure.phabricator.com/D12751