avocado: Refer to 'debug log' as 'job log'

Instead of using 'debug log' we can use 'job log', as it
is a human readable log of the job execution.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Set 'INTERRUPTED' status for interrupted tests

If we press Ctrl+C, the test that was being executed
still does not have a status, and that reflects in the
job log with a None printed in the final status.

So, if there's no status yet, we should safely (?)
assume that the test was interrupted.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>