Phedex node name returned by listFileBlockLocation

first iteration, fixes #5167

@ticoann I have made the pull request now as it may be easier to have a conversation with the changes available. Also I recall you said it's easier for you to track as a pull request.

Cheers
Alex
I actually don't know if the replica dict has a 'node' key as I couldn't find a description of what the data in the dictionary should look like. Please let me know if this key doesn't exist.