examples: commented-out path printing for Esther

I'm trying to clean up the core code while not causing too much trouble
to our users. Esther pointed out that there's an internal use case at
Orange where people are looking at the incremental results when
computing paths.

I strongly dislike commented-out debugging code, but for the sake of
progress, let's put it in here. It's roughly as good as that unused
`show` parameter, and it allowed a refactoring to make the code more
readable.

examples/path_requests_run.py

@@ -167,6 +167,7 @@ def compute_path_with_disjunction(network, equipment, pathreqlist, pathlist):
         if total_path :
             if pathreq.baud_rate is not None:
                 total_path = propagate(total_path,pathreq,equipment)
+                # for el in total_path: print(el)
                 temp_snr01nm = round(mean(total_path[-1].snr+lin2db(pathreq.baud_rate/(12.5e9))),2)
                 if temp_snr01nm < pathreq.OSNR :
                     msg = f'\tWarning! Request {pathreq.request_id} computed path from {pathreq.source} to {pathreq.destination} does not pass with {pathreq.tsp_mode}\n' +\