Submissiondata API endpoint shows duplicates if students submitted as a group

[oseppala]

If a submission is made in a group and the group contains N members The same submission is shown through the submissiondata API endpoint N^2 times

This can only be seen when best=no

See submission no. 1854 in the following: https://minus.cs.aalto.fi/api/v2/courses/169/submissiondata/?exercise_id=34199&format=json&best=no