Add the '-cc' option to the aprun command.

With the aprun default of '-cc cpu', we only get kernel scheduling
affinity with a single KNC CPU.  In order to get scheduling affinity
with all of them, we need to give some other option.  The '-cc none'
we give on other Cray system compute nodes seems to work fine for
this.

While here, I also removed some trailing white space on one line.
Merge pull request #583 from gbtitus/knc-aprun-needs-cc-none

Add the '-cc' option to the aprun command.

With the aprun default of '-cc cpu', we only get kernel scheduling
affinity with a single KNC CPU. In order to get scheduling affinity
with all of them, we need to give some other option. The '-cc none'
we give on other Cray system compute nodes seems to work fine for
this.

While here, I also removed some trailing white space on one line.
SLURM doc updates
Merge pull request #585 from vasslitvinov/adjust-readmes-for-SLURM-launcher

SLURM doc updates

* Added the requirement to set CHPL_LAUNCHER_WALLTIME for slurm-gasnetrun_ibv launcher.

While there:

* Noted that CHPL_LAUNCHER gets set to none when slurm and aprun are both in user's path.

* Streamlined slurm notes.

* Tweaked the formatting of how CHPL_LAUNCHER is chosen by default.

Reviewed by Elliot.
Add a note about ugni memory registration and concurrency with slurm.
Merge pull request #587 from gbtitus/doc-slurm-ugni-mem-registration-issue

Add a note about ugni memory registration and concurrency with slurm.

Reviewed by Thomas.
Fix nondeterministic output from walkdir() by requesting sorted output
Merge pull request #590 from bradcray/fix-filerator-regression

Fix nondeterministic output from walkdir() by requesting sorted output

[trivial, not reviewed]

I forgot to request sorted output in my new test yesterday, which
resulted in nondeterministic behavior across file systems/machines.
This broken in one configuration last night (and could break in others
over time).