Decrease boot timeout in the test suite

Originally created by @intrigeri on #11449 (Redmine)

Currently we wait up to 30 minutes:

  @screen.wait('TailsGreeter.png', 30*60)

… which makes the (failing) test suite runs on feature/stretch take many hours, because the Greeter fails to appear there.

AFAIK nobody runs the test suite in nested virtualization on slow hardware anymore, and even if they tried, I bet that lots of other things would be broken. IMO we should not bother trying to support this non-existing use case.

So I propose we lower that timeout to e.g. 5-10 minutes, or rather N times what we commonly see on Jenkins (say N=3 to be on the safe side).

Feature Branch: test/11449-decrease-boot-timeout

Related issues

• Has duplicate #11546 (closed)