Documentation and example for JMeter Sampler with MongoDB

[eliflores]

And fix a linting issue.

Note: This is related to the changes in the kangal-jmeter image, PR https://github.com/hellofresh/kangal-jmeter/pull/28.

[codecov-commenter]

Codecov Report

Merging #247 (4a56953) into master (bcedc5a) will decrease coverage by 0.98%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #247      +/-   ##
==========================================
- Coverage   56.87%   55.88%   -0.99%     
==========================================
  Files          37       37              
  Lines        4032     4103      +71     
==========================================
  Hits         2293     2293              
- Misses       1615     1686      +71     
  Partials      124      124              

Impacted Files	Coverage Δ
pkg/proxy/proxy.go	78.72% <0.00%> (-6.93%)	:arrow_down:
pkg/kubernetes/client.go	83.75% <0.00%> (-6.80%)	:arrow_down:
cmd/controller.go	20.37% <0.00%> (-2.08%)	:arrow_down:
pkg/controller/loadtest.go	2.99% <0.00%> (-0.18%)	:arrow_down:
cmd/proxy.go	0.00% <0.00%> (ø)
pkg/proxy/server.go	0.00% <0.00%> (ø)
pkg/controller/metrics.go	0.00% <0.00%> (ø)
pkg/controller/controller.go	0.00% <0.00%> (ø)

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[s-radyuk]

I think, with the latest release we should update this doc too because users should create their jmx tests with the same version of JMeter that Kangal uses.