Quantize glidein shutdown times in the cloud
Many clouds have quantized pricing for fixed time intervals -- for example, in EC2 if you run for 1 minute you may as well run for 60.
We should adjust the glidein lifecycle to maximize the value.
Example: An EC2 glidein job runs for 50 minutes. (The glidein is set to wait 20 minutes before retiring).
Since we would retire at 70 minutes, we should extend the glidein lifetime to roughly 120 minutes, since we've already paid for that hour.