Add indication to merge request list item that MR cannot be merged automatically

I often have the list of merge requests authored by me open to see which have failing builds, i.e. which still need some kind of action before they can be merged. On MRs that have been open for a while, a push to master can introduce conflicts, which also requires action from me (or the merger), which I am not currently notified of. This MR makes this information available from the MR list.