make changes.

Continuation of 69ed08cd

Bug 4033

Will set the DISPLAY variable in the adopted process automatically
if the job has an active forwarding session.

Returns display for X11 forwarding, or zero if forwarding
is not setup.

Bug 4120

srun --x11 will default to requesting X11 forwarding from
all nodes on a new allocation.

srun --x11 is ignored within an existing job allocation,
as the X11 forwarding must be setup by the prolog which
will have already run.

salloc --x11 will default to requesting X11 forwarding from
all nodes.

sbatch --x11 will default to requesting X11 forwarding from
the batch host only.

The pack_node_list may not be ordered across multiple components, which can
  cause problems for some MPI implementations. Put the pack_node_list records
  in alphabetic order and reorder pack_task_cnts pack_tids to match

Previously the accounting sometimes recorded the job, but not the
  short lived step. It is working consistently for me now.

Problem found by test1.65

Add support for specialized cores with task/affinity plugin (previously
    only supported with task/cgroup plugin).
Add "TaskPluginParam=SlurmdOffSpec" option that will prevent the Slurm
    compute node daemons (slurmd and slurmstepd) from executing on specialized
    cores.
bug 3337

CID 177245, 177246.

Coverity CID 177244

When a job array record is split, add the new record to the
  federation job table.
bug 4033

Utility functions for new x11 forwarding implementation.

Requests the allocated port only be available to localhost.
Follow through with the locations in the API using this, which
all need to be marked as 'false'.

Grab this so we can start using it elsewhere. Rename command
from run_script to run_command (there is already a different
run_command in the slurmd/common code that lead to conflicts).

Also grab _free_script_argv while here, and make sure we can still run
the same shutdown commands the Cray plugin relied on as before.

Previously these would show as jobid and jobid.4294967295.

While here tweak the log_set_fpfx function to take in an
xmalloc'd string directly, rather than clone it again.

Revert part of commit b0e6d3c3