Handle connection reset error in fast http client

[bendizen]

fix unhandled exception "ConnectionResetError: [Errno 104] Connection reset by peer"

[codecov]

Codecov Report

Merging #1475 into master will decrease coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1475      +/-   ##
==========================================
- Coverage   81.30%   81.22%   -0.09%     
==========================================
  Files          27       27              
  Lines        2386     2386              
  Branches      366      366              
==========================================
- Hits         1940     1938       -2     
- Misses        353      354       +1     
- Partials       93       94       +1     

Impacted Files	Coverage Δ
locust/contrib/fasthttp.py	85.44% <100.00%> (ø)
locust/user/task.py	95.67% <0.00%> (-1.09%)	⬇️

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