Permit more batch requeues for cloud bursting

If a batch job launch to the cloud fails, permit an unlimited
number of job requeues. Previously the job would abort on the
second launch failure.
if DOWN node set to PowerDown, clear NoResp flag

Without this change, a node in the cloud that failed to power up,
would not have its NoResponding flag cleared, which would prevent
its later use. The NoResponding flag is now cleared when manuallly
when the node is modified to PowerDown.
Avoid duplicate PowerUp of node on slurmctld start

This fixes a race condition if the slurmctld needed to power up
a node shortly after startup. Previously it would execute the
ResumeProgram twice for effected nodes.