Fix return code handling in the src/api/signal.c code.

which was causing build problems.  (Using srun_job_t in src/common was
not a good idea anyway.)

Remove debugging messages

    of SlurmdTimeout and SlurmctldTimeout for communications to slurmd and
    slurmctld daemons repsectively.

just keep trying.

function of this setting in the slurm protocol.

Eliminate redundant and incorrect "enum distribution_t" in env.h and replace
it with "enum task_dist_states" from slurm.h.  distribution_t was causing
the following inconsistency:

morrone:~$ srun -N3 -n6 -l env |grep SLURM_NODEID |sort
0: SLURM_NODEID=0
1: SLURM_NODEID=0
2: SLURM_NODEID=1
3: SLURM_NODEID=1
4: SLURM_NODEID=2
5: SLURM_NODEID=2
morrone:~$ srun -N3 -n6 -A
morrone:~$ srun -l env |grep SLURM_NODEID |sort
0: SLURM_NODEID=0
1: SLURM_NODEID=1
2: SLURM_NODEID=2
3: SLURM_NODEID=0
4: SLURM_NODEID=1
5: SLURM_NODEID=2