Fixes #10130

Signed-off-by: Damien Regad <damien.regad@merckgroup.com>

Improve performance of code building the list of users for all projects
introduced in commit 21746dd.

By using an associative array, the foreach loop to remove duplicates can
be simplified (no need for an if statement) and we can also remove the
current user from the list more easily.

Affects issue #10130

Since there is a [myself] value in the list, the current user should be
removed. This was done for ALL_PROJECTS with the fix for issue #10130,
but the single-project code still listed the current user.

By moving the code to remove the current user to the foreach loop that
builds the sort arrays, we ensure that it is removed in both cases.