Ensure the returned exit status is non-zero if we fail to map
If no -np is given, but either -host and/or -hostfile was given, then error out with a message telling the user that this combination is not supported.
If -np is given, and -host is given with only one instance of each host, then default the #slots to the detected #pe's and enforce oversubscription rules.
If -np is given, and -host is given with more than one instance of a given host, then set the #slots for that host to the number of times it was given and enforce oversubscription rules. Alternatively, the #slots can be specified via "-host foo:N". I therefore believe that row #7 on Jeff's spreadsheet is incorrect.
With that one correction, this now passes all the given use-cases on that spreadsheet.
Make things behave under unmanaged allocations more like their managed cousins - if the #slots is given, then no-np shall fill things up.
Fixes#1344
503e1274a9