Fix Cray NHC spawning on job requeue. Previous logic would leave nodes
allocated to a requeued job as non-usable on job termination.

Specifically, each job has a "cleaning/cleaned" flag. Once a job
terminates, the cleaning flag is set, then after the job node health
check completes, the value gets set to cleaned. If the job is requeued,
on its second (or subsequent) termination, the select/cray plugin
is called to launch the NHC. The plugin sees the "cleaned" flag
already set, it then logs:
error: select_p_job_fini: Cleaned flag already set for job 1283858, this should never happen
and returns, never launching the NHC. Since the termination of the
job NHC triggers releasing job resources (CPUs, memory, and GRES),
those resources are never released for use by other jobs.

Bug 2384