TTL job iteration will iterate the last item for multiple times

[YangKeao]

The code of TTL includes this pattern:

for _, job := range m.runningJobs {
    ...
    m.removeJob(job)
    ...
}

It will have two bad effects:

1. Some jobs will be skipped during one iteration. If the 4th job is removed, the 5th job will not be iterated.
2. The last job will be iterated for multiple times.

The best practice (IMO) to solve this issue is to reverse interating:

for i := len(m.runningJobs) - 1; i >= 0; i-- {
    ...
    m.removeJob(job)
    ...
}