Fix issue with task/affinity oversubscribing cpus erroneously when
using --ntasks-per-node.

This is related to bug 1145.  What was happening is all the cpus were
allocated on one socket instead of a cyclic method.  While this is allowed
it is strange and resulted in this bug.  There appears to be a different
bug as to why the tasks were laid out in a block fashion in the first
place.
Fix misleading comments.  These represent a core mask, not CPU.