Always show merge status

Always show the merge status of a merge request, even if the user has no
permission to do the actual merging.

Fixes
http://feedback.gitlab.com/forums/176466-general/suggestions/5673321-everyone-should-be-able-to-see-a-mr-status
Merge pull request #6634 from jvanbaarsen/see-merge-status-no-permission

Always show merge status