All GATK tools at http://usegalaxy.org have been deprecated and are no longer supported. I don't think that the tool authors of the updated GATK tools in the Tool Shed (for a local or cloud Galaxy) are supporting these tools anymore either, due to licensing and other complications.
Instead, we suggest using alternative methods/tools for variant analysis. Please see the tutorials here: https://galaxyproject.org/learn/
Thanks, Jen, Galaxy team