Retry on plagiarism backend errors

[tcibinan]

It would be nice to have some retry policy to handle plagiarism backend errors. The following retry algorithm can be of help here:

1. Try to perform plagiarism analysis.
2. Wait for some time if the plagiarism analysis fails.
3. Try to perform plagiarism analysis once again.
4. Wait for some more time if the plagiarism analysis has failed again.
5. Try to perform plagiarism analysis again and again with bigger timeouts until the number of allowed retries is reached or some of the analyses finishes successfully.

FYI currently MOSS doesn't really works pretty well. It seems that a lot of researches use the tool during the coronavirus crisis and can't handle all the requests. MOSS server resets some connections from time to time. Moreover the average analysis duration is increased by 5-10 times. According to the moss official page they are awared about the problem but it doesn't seem to be resolved now.