Fix KNL feature reboot logic

Previous logic could trigger KNL node reboot when job did not
request any KNL MCDRAM or NUMA modes as features. For example:
srun -N3 -C "[foo*1&bar*2]" hostname
would trigger reboot of all KNL nodes even though no KNL-specific
features were requested. This bug only exists in v18.08 and was
introduced when expanding KNL node feature specification capabilities.