[nextest-runner] stop duration-based stress runs when exactly zero time remains

Fix a boundary case.

JJ: Change ID: ortqwquy
JJ: This commit contains the following changes:
JJ:     M nextest-runner/src/reporter/displayer/imp.rs
JJ:     M nextest-runner/src/reporter/events.rs
JJ:
JJ: Lines starting with "JJ:" (like this one) will be removed.
