Fix issue with squeue/scontrol showing correct node_cnt when only tasks
are specified.

This is a fix to commit b9cc5b31047 which just didn't know
mc_ptr->ntasks_per_core is initialized to INFINITE.  Without it the
node_cnt packed would be set to 1 on the user tools.

This fixes bug 1148.
Merge remote-tracking branch 'origin/slurm-14.03' into slurm-14.11