Treat a JobLeaseDuration of 0 the same as no lease. HTCONDOR-960
Treat a JobLeaseDuration of 0 the same as no lease. HTCONDOR-960

The docs say setting job_lease_duration=0 means there's no job lease,
and JobLeaseDuration will be undefined in the job ad. In fact, this ends
up setting JobLeaseDuration=0 in the job ad. Let's just treat both the
same.

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