support maximum number of simultaneously running tasks

[jeroendecroos]

For Slurm we can set the maximum number of simultaneous running tasks for an array job as follows:
--array={start}-{end}:{step-size}%{maximum number of simultaneously running tasks}

But it seems slurm-drmaa doesn't support this:

slurm-drmaa/slurm_drmaa/session.c

Line 123 in 665d5b5

job_desc.array_inx = fsd_asprintf( "%d-%d:%d", start, end, incr );