postgres:upgrade doesn't appear to respect flags

[iandees]

Description of problem

I tried to postgres:upgrade to a specific image that contains PostGIS, but it didn't seem to work. Here's the trace when it happened.

This seems to be related to whether the image has been pulled or not. I don't have a reliable way of reproducing it, though. I was working on this with @josegonzalez and he said I should file a ticket with the trace above.