select/cons_res: minor improvement in logging
Improve GRES support for CPU topology

Previous logic would pick CPUs then
reject jobs that can not match GRES to the allocated CPUs. New logic first
filters out CPUs that can not use the GRES, next picks CPUs for the job,
and finally picks the GRES that best match those CPUs.
bug 410
Fix for job requesting GRES on node that lacks any GRES

Previous logic would allocate job resources on such a node
rather than reject the job allocation on that node.