Run pre_run after persistent buffer creation per Cray documenation

Add logic to burst_buffer/cray and generic to set job's buffer size
  in TRES array for limits and accounting. This includes only the
  the job-specific buffers, not persistent buffers, which will be
  handled separately.

The problem is that with high rate profiling, the cpu usage becomes a
binary field (see the output below). I would like to have a more accurate
value of the cpu usage. I'm thinking about writing another profiling
plugin that may be very useful in our environment, and probably also in
other environments where compute nodes are shared.

Bug 1748

change is to ease future transition to IPv6 reducing the number of
places that use AF_INET.  AF_SLURM currently points to AF_INET though.

char in the tres string.

removed, so make sure we process correctly, sort it while we are at it.

slurmdb_combine_tres_strings.

Bug 858

Plus some cosmetic changes to a couple of tests

end up pointing to qos_ptr_2 erroneously.

clearing the pointer in the partition record.

Fix case where job would get the wrong cpu count when using --ntasks-per-core and --cpus-per-task together.

Bug 1370

Bug 1295
Continuation of 166a4eb8

We are using a non-default AuthInfo configuration and based on
log-messages we see I believe this is not properly handled in certain
parts of the code.

Typical log message:
Aug 12 17:06:15 t02n20 slurmd[27001]: error: Munge encode failed:
Failed to access "/var/run/munge/munge.socket.2": No such file or
directory
Aug 12 17:06:15 t02n20 slurmd[27001]: error: Creating authentication
credential: Socket communication error
Aug 12 17:06:15 t02n20 slurmd[27001]: error: stepd_connect to 3165.0
failed: Protocol authentication error
Aug 12 17:06:15 t02n20 slurmd[27001]: error: If munged is up, restart
with --num-threads=10

Unfortunately the reservation's core_bitmap is a global bitmap and the nodes
in the system may have changed in terms of their node count or nodes have been
added or removed. Make best effort to rebuild the reservation's core_bitmap
on the limited information currently available. The specific cores might
change, but this logic at least leaves their count constant and uses the
same nodes
bug 1850

Add logic to get default account/qos information for newly discovered
  buffers in order to properly enforce limits.
Add logic to get TRES index for limits
Refactor bb_find_user_rec() function argument