task/affinity using cpusets logic added, from Don Albert, Bull.

    Cpuset libary must be installed and set "TaskPluginParam=cpusets"
    in slurm.conf to enable.
    NOTE: Currently disabled until additional testing is performed. 
    Enable by changing "HAVE_CPUSETTS_EXP" to "HAVE_CPUSETS" in
    src/plugins/task/affinity/*.[ch].