Expand documentation for chosloc config parameter

doc/man/man5/slurm.conf.5

@@ -374,7 +374,15 @@ for use with IBM POE (Parallel Operating Environment) only
 
 .TP
 \fBChosLoc\fR
-The fully qualified pathname of the chos command if the Chroot OS tool is used
+If configured, then any processes invoked on the user behalf (namely the
+SPANK prolog/epilog scripts and the slurmstepd processes, which in turn spawn
+the user batch script and applications) are not directly executed by the slurmd
+daemon, but instead the \fBChosLoc\fR program is executed.
+That program's argument are the program and arguments that would otherwise be
+invoked directly by the slurmd daemon.
+The intent of this feature is to be able to run a user application in some
+sort of container.
+This option specified the fully qualified pathname of the chos command
 (see https://github.com/scanon/chos for details).
 
 .TP