Reverts code added in 8486c97e to handle failure mode of BGQ jobs.

Bug 6566.

The int size may not be enough when converting from seconds to usec for the
maximums defined for bf_interval. _yield_sleep has been to adapt to this change
too.

Bug 6401

All numeric backfill parameters have now maximums and minimum values.

Bug 6401

Improve log and comments

Set CUDA_VISIBLE_DEVICES and CUDA_MPS_ACTIVE_THREAD_PERCENTAGE environment
variables in Prolog and Epilog for jobs requesting gres/mps. This can be
used to start, terminate and otherwise manage mps servers for the user.

Previous logic would drain node with less than configured gres.
bug 6635

This also removes the check for duplicates that seemed redundant.

Bug 6635

Without this change a single job could not use 100% of the gres/mps on
any single device, but only up to one less than the total count.

bug 6635

Without this change, test19.18 would generate fatal errors due to
using the Slurm APIs, but not having the same environment as the
slurmctld

as the parameter to determine how to gather gres/gpu configuration.
bug 6635

Commit 6ac4ce84 introduces a dependency in the gres plugin
on the select plugin.

Bug 6638.

slurmstepd needed some changes to avoid creating a size zero bitmap.
bug 6635

If we do have 0 this means we have no gres on the node.

Any other call to the bitstring will fail (bit_test, bit_clear, etc).

I was unable to find a situation where this would be valid.

Bug 6616

Bug 6612

All of the buffers are 24 characters, require the input string is
less than 23 characters and null combined to be parsed.

Remove regression added in b9699c2f

Bug 6636.

Bug 6636.

This prevents some strange errors generated by select/cons_res

if job tries to reset gpu frequency and nvml is not supported then
log "GpuFreq=control_disabled". Test of this function recognizes
this and exits.

Contiuation of 9a243a1a

Bug 6592

Also mention FIXME's that need to be fixed with this code.

Generated by autoreconf, should never be checked in.