Updated xctool to clean up and merge output XML.

Addressing issue: https://github.com/facebook/xctool/issues/141
xctool, upon supplying different testsuite objects with the same name,
would separate the testsuites. This diff should merge the xml objects
that should not be logically separated.
Merge branch 'sameen/xctool_junit_reporter' of github.com:sameenjalal/xctool into sameen/xctool_junit_reporter