We had a node with a Slurm reservation so that it's state was "reserved". This state is not understood by node-mark-online:
20170711 16:05:45 [slurm] /usr/libexec/nhc/node-mark-online h001
/usr/libexec/nhc/node-mark-online: Not sure how to handle node state "resv" on h001
/usr/libexec/nhc/node-mark-online: Skipping resv node h001 (none )
It seems to me that this could be solved by changing /usr/libexec/nhc/node-mark-online
77c77
< alloc*|comp*|idle*|mix*|resume*|undrain*|resv*)
alloc*|comp*|idle*|mix*|resume*|undrain*)