Redirect to main merge request page if no conflicts

Description

When navigating to the /conflicts page of any merge request, check if there are any conflicts on the merge request. If there are no conflicts, then just redirect to the main merge request page.
The /conflicts link is only accessible in the mr widget when there are conflicts. So accessing this page when there are no conflicts at all is an edge case. It can happen if somehow there is an error between BE and FE during conflict resolution or if you somehow directly access the /conflicts page directly by pasting it in the URL of your browser. Otherwise, right now, when you resolve a conflict, you are already redirected to the main merge request page.
Remove the existing copy right now, and clean up any other existing code that will no longer be needed. (See original description below.)

It is awesome we can resolve conflicts in MRs directly from the GitLab UI. But after we did it, we get this sentence:

The merge conflicts for this merge request have already been resolved. Please return to the merge request.

But there is no link to come back to the MR.

Add a link to go back to the MR main view as an hyperlink to that text.

Edited May 31, 2018 by Victor Wu