Add section for the Origin to the troubleshooting guide

[aowen-uwmad]

In a previous PR, @jhiemstrawisc suggested some more specific steps for troubleshooting the Origin. Changes were too much for that PR, but is a good suggestion for future work.

• Add a new subsection to the Federating Data section of the troubleshooting guide.
• Detail how to check if an origin is online at all
• Detail how to check if an origin is discoverable by the director
• Anything else that seems important to include right away