Enforce test duration across reboots and restarts #4492
Description
Tests that triggered reboots and restarts were given their full duration on every invocation. This behavior is most likely incorrect, a duration should apply to the whole test, no matter how many times it reboots a guest.
Patch adds Duration object which poses a strict deadline, derived from the test duration key. Unlike a timeout, it is not reset after guest reboot or test restart.
Fixed by #4416