Add p99.9 and p99.99 to request stats distribution csv

[cyberw]

Solves #1040

[heyman]

Nice! Wouldn't mind a line about this in the Documentation's Changelog either (changelog.rst).

[heyman]

Currently this PR also changes the percentile stats that is outputted to the console when the test finishes in --no-web mode. That's why the tests are failing I think.

[codecov]

Codecov Report

Merging #1125 into master will not change coverage.
The diff coverage is 66.66%.

@@           Coverage Diff           @@
##           master    #1125   +/-   ##
=======================================
  Coverage   74.47%   74.47%           
=======================================
  Files          18       18           
  Lines        1802     1802           
  Branches      269      269           
=======================================
  Hits         1342     1342           
  Misses        393      393           
  Partials       67       67

Impacted Files	Coverage Δ
locust/stats.py	82.04% <66.66%> (ø)	⬆️

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[cyberw]

Won't the change log get the ticket added automatically?

[heyman]

Won't the change log get the ticket added automatically?

It will be added to the auto-generated CHANGELOG.md, but the Changelog Highlights in the documentation is manually curated: https://docs.locust.io/en/latest/changelog.html

[cyberw]

@heyman Ok to merge?

[heyman]

Yes! Nice!