Add PriorityFlags value of "TICKET_BASED".

On job step launch failure, the function
"slurm_step_launch_wait_finish()" will be called twice in launch/slurm,
which causes srun to be aborted:

srun: error: Task launch for 22495.0 failed on node cn6: Job credential
expired
srun: error: Application launch failed: Job credential expired
srun: Job step aborted: Waiting up to 2 seconds for job step to finish.
cn5
cn4
cn7
srun: error: Timed out waiting for job step to complete
srun: Job step aborted: Waiting up to 2 seconds for job step to finish.
srun: error: Timed out waiting for job step to complete
srun: bitstring.c:174: bit_test: Assertion `(b) != ((void *)0)' failed.
Aborted (core dumped)

The attached patch(version 2.5.1) fixes it. But the message of
"
Job step aborted: Waiting up to 2 seconds for job step to finish.
Timed out waiting for job step to complete
"
will still be printed twice.

Correction to CPU allocation count logic in for cores without hyperthreading.

With jobs launched using srun directly which end abnormally, there will
be a step-killed-message(slurmd[cn123]: *** 1234.0 KILLED AT ... WITH
SIGNAL 9 ***) from each node. And/or there will be a
task-exit-message(srun: error: task[0-1]: Terminated) for each node. For
large scale jobs, these messages become tedious and the other error
messages will be buried. The attached two patches(for slurm-2.5.1)
introduce two environment variables to control the output of such
messages:

SLURM_STEP_KILLED_MSG_NODE_ID: if set, only the specified node will
print the step-killed-message;

SLURM_SRUN_REDUCE_TASK_EXIT_MSG: if set and non-zero, successive task
exit messages with the same exit code will be printed only once.

With jobs launched using srun directly which end abnormally, there will
be a step-killed-message(slurmd[cn123]: *** 1234.0 KILLED AT ... WITH
SIGNAL 9 ***) from each node. And/or there will be a
task-exit-message(srun: error: task[0-1]: Terminated) for each node. For
large scale jobs, these messages become tedious and the other error
messages will be buried. The attached two patches(for slurm-2.5.1)
introduce two environment variables to control the output of such
messages:

SLURM_STEP_KILLED_MSG_NODE_ID: if set, only the specified node will
print the step-killed-message;

SLURM_SRUN_REDUCE_TASK_EXIT_MSG: if set and non-zero, successive task
exit messages with the same exit code will be printed only once.

User root or SlurmUser don't need valid sbcast credential

This can be useful for testing purposes

Used to specify the communication protocol to be used for ALPS/BASIL.