sched/backfill: Reset job time limit if needed for deadline scheduling.
bug 5183

- validate more GRES limits
- merge generic parameters
  generic (e.g. "gpu") cpus-per-tres and mem-per-tres values
  will be merged as needed to type-specific (e.g. "gpu:volta")
  specifications.

Do not allow Operators to set this at submit time.

Bug 5306.

I do not see a use for this syntax, especially given that it appends
an extra comma in between the two halves. Only allow the full string
to change to put this in line with the Comment handling.

Remove special handling of an identical AdminComment as well,
since the end result is unchanged, and this avoids a potentially
expensive xstrcmp call.

Bug 5306.

These applied further below, but have been superceeded
by a better commend anyways.

Coverity CID 186551 and 186556

Coverity CID 186552

Identical problem in 3 related functions.
Coverity CID 186550,186553, 186554

Note there was a bug in the configuration parsing logic to get
the partition's DefMemPerGPU (it was stored in the field for
DefCpuPerGPU).

Bug 5286

RHEL 6 (and related) use lua as the package name, test
if that package exists with a version >= 5.1 if the other
tests have already failed.

Bug 5263.

This avoid queueing jobs that can not run due to a gres limit.

This was missed when committing before.

Bug 4506

Bug 4506

accrue_time instead of anything else.

Bug 4506

Bug 4506

This will be needed in a future commit.