Assignment policy

Still some errors when assigning jobs with multiple level of task groups.
To avoid throttling assignment, we lifted a restriction in iterating through the nodes.
However it raised another pb in thefoldernode iterator ("while True" loop)
To avoir looping indefinitely we change the while condition:
 - we do not loop until readyCommandCount=0 (because with ram limit it can not decrease to 0)
 - instead we loop until readyCommandCount=0 or enough iteration done already (i.e. loop count >= readycommand)