I've updated the TestToolsTask that supports using test containers, in addition to the test metadata files supported by v1. Unfortunately, the task I posted originally didn't result in builds being marked as failed when the tests had errors. I missed that fact in my testing. The reason for the problem is that the v1 Team Build logger looks for the task name, TestToolsTask, and the power toy task was originally called TestToolsTaskEx. With this new release, the task has the same name as the original v1 task, so that builds will be marked as failed when the tests fail.
If you downloaded the original release, you simply need to copy the Microsoft.TeamFoundation.Build.targets and Microsoft.TeamFoundation.PowerToys.Tasks.QualityTools.dll files from the zip to get the fix (see the Word doc for the paths).
Thanks to Thomas for pointing out this bug!
The updated version is attached to the original post. I apologize for the inconvenience.