fix(http): superfluous response.WriteHeader call

[rustatian]

Reason for This PR

• superfluous response.WriteHeader call

Description of Changes

• Do not try to write into response writer if the pipe had been interrupted.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

[Author TODO: Meet these criteria.] [Reviewer TODO: Verify that these criteria are met. Request changes if not]

• [x] All commits in this PR are signed (git commit -s).
• [x] The reason for this PR is clearly provided (issue no. or explanation).
• [x] The description of changes is clear and encompassing.
• [x] Any required documentation changes (code and docs) are included in this PR.
• [x] Any user-facing changes are mentioned in CHANGELOG.md.
• [x] All added/changed functionality is tested.

[codecov[bot]]

Codecov Report

Merging #80 (b305fa3) into master (cdd2080) will decrease coverage by 0.37%. The diff coverage is 72.00%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
- Coverage   68.98%   68.60%   -0.38%     
==========================================
  Files         118      118              
  Lines        9920     9925       +5     
==========================================
- Hits         6843     6809      -34     
- Misses       2403     2443      +40     
+ Partials      674      673       -1     

Impacted Files	Coverage Δ
http/handler/handler.go	85.89% <72.00%> (+0.74%)	:arrow_up:
jobs/listener.go	35.15% <0.00%> (-12.50%)	:arrow_down:
sqs/item.go	65.78% <0.00%> (-7.24%)	:arrow_down:
websockets/executor/executor.go	62.87% <0.00%> (-5.31%)	:arrow_down:
jobs/metrics.go	95.91% <0.00%> (-4.09%)	:arrow_down:
beanstalk/item.go	77.14% <0.00%> (-2.86%)	:arrow_down:
jobs/plugin.go	61.35% <0.00%> (-0.49%)	:arrow_down:

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