Batch job will have environment variable set: "SLURM_CPU_FREQ_REQ=0"
and this will be loaded and reported as an invalid value by srun.

This addresses trouble ticket 85

runjob_mux

is always set when sending or receiving a message.

Conflicts:
	doc/html/high_throughput.shtml

Without this change the values known to slurmctld do not change without a cold-start.

than 1 midplane but not the entire allocation.

multi midplane block allocation.

where other blocks on an overlapping midplane are running jobs.