Add output when gtest compatible XML output is requested.
Add output when gtest compatible XML output is requested.

Will help debug an issue with the test flakiness dashboard. This is only used
on the main waterfall and not on the try slaves.

TBR=csharp@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/12212017

git-svn-id: d5a9b8648c52d490875de6588c8ee7ca688f9ed1@180725 0039d316-1c4b-4281-b951-d872f2087c98

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py