fix conflicts window shows blank screen for long time

This issue was observed in Sharp Desktop Sync Client which is using nuxeo-drive. The problem should also be present in nuxeo-drive.

1. Drive: Install and configure drive with a user account
2. DM: Login to server as same user
3. DM: Configure the folder for sync by drive (register as sync root)
4. DM: Share the same folder to other users.
5. Drive: upload some files to the shared folder.
6. Drive / DM: The local user (Drive) and another user (DM) edit the same file in parallel.
7. Drive: drive detects conflict when trying to upload the local changes, so the conflicts can be seen in conflicts window.
8. repeat previous two steps (6,7) with different user account combinations
9. Now there are many conflicts in Drive and each last contributor is different.
10. Exit Drive and launch it again.
11. Open conflicts window.
    Result: The conflicts window shows blank page for sometime.
    The duration the window shows blank page is because drive is trying to resolve the last contributor userid to full name of last contributor.
    1. If connection between drive and server is fast, then the blank page is displayed for few seconds.
    2. if the connection between drive and server is slow, then the blank page shows for a few minutes giving the impression that the product has hanged.