Adam Kurkiewicz

`cmsImportUser --all` is slow for large number of users (~1000)

5

[ImportUser logic](https://github.com/cms-dev/cms/blob/master/cmscontrib/ImportUser.py) has O(n**2) performance with the `--all` flag, due to processing the entire list of users once per each user. This degrades performance of large user imports, with imports...