Needs to detect when autopkgtests have failed to even run

From time to time (typically associated with infra outages I guess?), what will happen is that autopkgtest runs will be aborted/lost/etc. Then what happens is that britney reports the tests as "in progress" but they do not appear anywhere on http://autopkgtest.ubuntu.com/running. This issue then cascades into bileto, which has no choice but to trust britney's "in progress" status, and users end up seeing "automated tests: running" stuck forever with no idea that something has actually gone horribly wrong.

It would be nice if britney could report an error that the test could not actually be confirmed to be running for real, so that we can identify sooner that there's a problem to fix. In the current instance of this, bileto user waited 14 hours before escalating the issue to me (considering that autopkgtests can sometimes take some hours, it does take people quite a long time before they finally realize that something must be wrong).