processes test: fail if anything raises "HIGH" or "CRITICAL"

It'd be nice to have an integration test for `scan --processes` that asserts a couple of things:

- ensure we have results for at least >8 processes
- ensure that no processes alert
- that the integration test is itself in the list of results (with no matches) 
- that the scan doesn't return an error code

As part of this we'll probably have to clamp down on false positives, but that's OK by me.