Description of the problem:
The pin-latest.py script should only perform pinning for image manifest tags
that are also pointed at by another persistent, unmoving tag. This is because
otherwise the sha we pin to may get garbage collected. This is not a problem
for assisted components because we have such persistent tag. But recently we
moved to using the postgres image from a quay organization outside of our
control. That organization doesn't not have a persistent tag for every manifest
the `:latest` tag happened to be on, so we can not do pinning for the postgres
image. Pinning postgres is not too important anyway because it's very stable.

Release version:
N/A

Operator snapshot version:
N/A

OCP version:
N/A

Browser Info:
N/A

Steps to reproduce:
N/A

Actual results:
pin-latest.py pins the postgres image and as a result

Expected results:
pin-latest.py should not pin the postgres image

Additional info: