Summary

Permission scheme is linking wrong user who had username renamed and the original username is reused by other account.

Steps to reproduce

1. Create a user with username first.
2. Rename the username to second.
3. Create another user with username "first" again.
4. Go to JIRA permission scheme.
5. Grant any permission(single user) to the user first.
6. Observe the user for that permission - user second will be there.

Current Result

User second is the one that is linked to the permission.

Expected Result

User first should be the one linked to the permission.