Step restart may not work with many workers and long run times

With multiple workers and long simulation run times, only half of the workers wake up after the step restart.

I am including the "dummy_simulation.txt" spec and the "workers.txt" batch script. To reproduce the problem on a system with slurm, type:

merlin run dummy_simulation.txt
sbatch workers.txt

and, as soon as the job has started running and the tmp_restart_test_*/dummy*/* subdirectories have been created, type

more tmp_restart_test_*/dummy*/*/*log

and count how many samples reported "Restarting". All 8 samples should restart but only 4 of them do.

Description of the workflow:
-run a "sleep 1" simulation
-restart (after a one-second delay)
-print a line including "Restarting"
-run a "sleep 200" simulation
-terminate: none of the restarted "sleep 200" simulations should finish since the allocation is set to die after 3 minutes.

However, if the "merlin resources" block is removed from the spec, and the test is repeated, all 8 samples report "Restarting", as expected. It may be worth comparing the celery command that is executed in these two scenarios.

dummy_simulation.txt
workers.txt

Start with the attached dummy_simulation.txt and workers.txt files, then run merlin run dummy_simulation.txt and sbatch workers.txt on a Slurm system. Inspect the generated logs for Restarting and compare the Celery command in runs with and without the merlin resources block; done means all 8 samples restart as expected.