Fix MaxRunSchedTime to cancel Job in time.

Modified the code so MaxRunSchedTime will use the new
initial_sched_time when checking to see if a job should be canceled.

We have a set of jobs that we want to definitely end at a known
time - Z hours after they've been initially scheduled - no matter what
state the job is in.

Patch by Thomas Lohman from bacula devel mailinglist.