Reset node's CpuLoad more frequently

Reset a node's CpuLoad value at least once each SlurmdTimeout seconds.
Previously the value would not be reset unless communications with the
slurmd did not happen for at least 1/3 of the SlurmdTimeout value.
That means nodes that were actively running and terminating jobs would
not get the CpuLoad value reset in a timely fashion. Added a CpuLoad
reset timer to prevent this.
Correction for CpuLoad updates

This corrects logic in commit fae55cbe8226f7f620190d82b3d9af81bfd65307
to properly support front-end system configurations
schedule enhancement for reservation

Scheduler enhancements for reservations: When a job needs to run in
reservation, but can not due to busy resources, then do not block all jobs
in that partition from being scheduled, but only the jobs in that
reservation.
Export "SLURM*" env vars if --export=NONE

Previously if the sbatch --export=NONE option was used then several
Slurm environment variables were not propagated from the sbatch
command (SLURM_SUBMIT_DIR, SLURM_SUBMIT_HOST, SLURM_JOB_NAME, etc.)
Avoid env vars that are too long

See bug 644
Add -r to squeue --usage output

fix for bug 647
make error message more clear
CRAY/ALPS - Add support for CLE52
Merge remote-tracking branch 'origin/slurm-2.6'
When recovering node state if the Slurm version is 2.6 or 2.5 set the
protocol version to be SLURM_2_5_PROTOCOL_VERSION which is the minimum
supported version.
Update the scancel man page.
Update sacctmgr man page documenting how to modify account's QOS.
Fix issue where jobs still pending after a reservation would remain
in waiting reason ReqNodeNotAvail.
Update last_job_update when a job's state_reason was modified.

Some of these were resulting in the state of a job not being updated
correctly to tools like sview.
Minor debugging change, and cleaner initialization.
Free job_ptr->state_desc where ever state_reason is set.
Fix for sjstat which currently does not print >1TB memory values
correctly.
Pudate the NEWS file.
Don't return 1 if not ran as super_user, like the other tests.
Fixed sacct.1 and srun.1 manual pages which contains a hyphen where
    a minus sign for options was intended.