Rewrite pipeline-scanner to be compatible with overlay2 (without atomic mount)

[navidshaikh]

pipeline-scanner works by mounting image on localhost and running scanner against image's rootfs.
This workflow is not practical while using (recommended) overlay2 storage driver with docker as overlay2 doesn't support writable mounts needed by scanner.

This issue is to track, re-write of pipeline-scanner (along with rename yum-updates-scanner) to work without atomic mount option.

[navidshaikh]

This is also going to simplify running scanners within containers / openshift environment.

[dharmit]

This. Exactly what I was thinking since long but didn't want to bring up till we start working on new architecture. But at the moment we're using yum command which requires rw access. We need to figure a different way of getting the data we're interested in.

This would also apply to rpm verify scanner, no?

The discussion we had today about repo tracking and yum-update scanner overlapping in using similar data for their functionalities. I'd like us to think through this and come up with a plan that helps us solve all of yum-update scanner, rpm verify scanner and repo tracking in a way that doesn't require more rework. Even if that means we deprecate yum-update scanner in favor of reliable and stable repo tracking piece.