Add test case for stats_history

[taojy123]

No description provided.

[codecov]

Codecov Report

Merging #1538 into master will increase coverage by 0.42%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1538      +/-   ##
==========================================
+ Coverage   81.96%   82.39%   +0.42%     
==========================================
  Files          28       28              
  Lines        2562     2562              
  Branches      389      389              
==========================================
+ Hits         2100     2111      +11     
+ Misses        364      352      -12     
- Partials       98       99       +1     

Impacted Files	Coverage Δ
locust/clients.py	90.19% <0.00%> (-4.91%)	⬇️
locust/user/task.py	97.83% <0.00%> (+0.54%)	⬆️
locust/runners.py	84.57% <0.00%> (+1.33%)	⬆️
locust/stats.py	90.08% <0.00%> (+1.61%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update eabee23...70e6ef8. Read the comment docs.

[cyberw]

thanks!