Add user:group change function to set command to assign cpusets to different users.

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Normally you're required to be root to manipulate and exec/move processes into 
cpusets.  The hierarchy can be changed to a different owner, which will allow 
that user (and group) on the system to exec/move processes into those cpusets.  
Currently, this can be done outside cset by root (commonly done in a 
boot.cpuset type init.d file for example); however, this means that the path to 
the cpuset fs must either be hardcoded (in the script for ex.) or other 
mechanisms be used to figure it out.  It would be easier if this function was 
included in the cset set command since it already figures out where the cpuset 
fs is mounted (or mounts it if it's not).

Original issue reported on code.google.com by tsariou...@gmail.com on 15 Feb 2012 at 6:09