[libraries] Get examiner sites by UserID

[CamilleBeau]

Brief summary of changes

We found this bug on CCNA where if a user has the same full name as another user, the examiner sites from the other user will show up in the edit user page.

• Have you updated related documentation?

Testing instructions (if applicable)

1. Outside of this PR, Create 2 users with the same name
2. Set one user as examiner at multiple sites
3. Go to the other user, and see that the same sites show up as examiner
4. Try to remove the examiner sites and notice that you cannot
5. Checkout this PR and refresh the second user (without the examiner sites)
6. Now you should not see examiner sites where they are not meant to be

[driusan]

@CamilleBeau The tests on this are failing

[CamilleBeau]

@CamilleBeau The tests on this are failing

Fixed! Thanks

[shonibare]

LGTM