Be consistent in our handling of the "only HNP in allocation" case when setting up the VM. Thanks to Tetsuya Mishima for the suggestion.

cmr=v1.8:reviewer=rhc
Per patch from Tetsuya Mishima, do a nicer job of warning the user that we need to map to a higher level to get the number of requested cpus/rank. Also, change the mapping policy to "byslot" when falling back to that option.

cmr=v1.8:reviewer=rhc