Correct estimated job start time

sched/backfill: Correct job start time estimate with advanced reservations.
Under some conditions, the job start time would be set to the end time
of an advanced reservation that may have nothing to do with that job's
resource requirements.
bug 911
Revert vestigial logging

Remove some debugging logic accidentally included in commit
7a187f10de8cfcfcdfa9e3cd392e14389890c8f4