Reload with full diff links to json version

GitLab 7.13.4 7c3e8bc

Steps to reproduce:

• Navigate to a merge request that has more diffs than can safely be shown so you get the orange warning:

• Hover over the link "Reload with full diff" button
• Notice that the link is to the .json version, e.g.

http://my.server/group1/project1/merge_requests/42/diffs.json?force_show_diff=true

Whereas the link should be to:

http://my.server/group1/project1/merge_requests/42/diffs?force_show_diff=true