The patch http://review.whamcloud.com/#/c/12524/2 breaks mounts of MGS/MGT volumes with short names (which is valid for an MGS/MDT, since they do not have to include an index or the file system name).

[root@centss02 ~]# mount -t lustre -o abort_recov /dev/sdb /tmp/lustre/centss02/mgt
mount.lustre: invalid name 'MGS'

Since the entire purpose of that code is to fix up OST & MDT names to indicate their status, presumably the solution is to simply not call this check on the MGS/MGT volume.