Pelican plugin returns os.exit(11) on returnable errors, condor only wants os.exit(0)

[turetske]

When a pelican error is retryable, the plugin calls os.exit(11) - which is how we mark retryable errors. Condor devs want us to only mark the ad as retryable and exit with 0.

[matyasselmeci]

This change is going to cause a backward compatibility issue because our AP policy for retries currently depends on the return code being 11. How do the Condor devs plan on dealing with that?