Fail if container image cannot be scanned, unless specified

[pgesek]

Infrascan currently skips issues with Docker containers it scans, such as not being able to pull them.

This should result in a build failure by default - we should not hide problems related to such images due to Intermittent failures.

We should add an option, something like --ignore-missing-images , which can be used to optionally preserve the current behavior.