Needs more more to play nice with REQUEST_TERMINATE_ rpcs.

slurmstepd unix domain sockets, it will attempt to send a SIGKILL using
stepd_signal_container before unlinking the socket file.

It has been modified to work with the new slurmd/slurmstepd code layout.

UCRL-CODE-2002-040 to UCRL-CODE-217948. No changes 
in any logic.

return code, just report an error and abort.

UP -> up
DOWN -> down
UNLIMITED -> infinite

select/cons_res (could leave job in COMPLETING state 
indefinitely).

closes.