We can have jobs with a lower job timeout values, given by CI_JOB_TIMEOUT environment variable, such as the pytest ones. The previously hardcoded burst length of 1000 messages at a simulated rate of 1 msg/sec caused tests to exceed these timeouts and fail unexpectedly on specific job timeouts. Reported-by: Eric Engestrom <eric@igalia.com> Signed-off-by: Guilherme Gallo <guilherme.gallo@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34907>