Test metrics are not preserved on Stop click in the UI

[niconphantom]

Description of issue / feature request

In Locust 0.8.1, when Stop button is clicked in the UI, RPS, latency and other test metrics are frozen and preserved until # of users is changed and another test is performed.

In 0.9.0 this is not the case and when Stop is clicked, RPS and other counters slowly go down from let's say X RPS to 0 RPS. This is super inconvenient when manual testing is performed and the test metrics should be documented.

More than that, if I export a CSV with request details right after I click stop and then download the same file after X seconds, I see totally different numbers. So it takes some time for counters to reach 0 and each file download shows inconsistent result.

Expected behavior

Test metrics should be preserved in the UI and on CSV download once the Stop button was clicked.

Actual behavior

Test metrics slowly change from X to 0 in both UI and on CSV download.

Steps to reproduce (for bug reports)

1. Start any test with 1 master and X slaves on single machine with UI mode.
2. Open UI and start the test. Let it run for some seconds until you see RPS value > than 0.
3. Click Stop in the UI
4. Wait some seconds and you should see RPS and other metrics slowly changing from X to 0.

[cyberw]

Closing due to inactivity.

[heyman]

I just successfully reproduced this, and I do think it should be classified as a bug.

It's only reproducible when running Locust distributed.

[heyman]

Should be fixed by 3df524d.