Unit-test for network-bound collectors.

[Tatsinnit]

This PR adds unit-test for the network bound-collector, key motivation is to improve code base quality along with code-cov.

Thanks.

cc: @arnaud-tincelin 🙏☕️ & fyi: @rzhang628 and @qpetraroia

[codecov-commenter]

Codecov Report

Merging #110 (ff0dafc) into master (7e0b1a9) will increase coverage by 8.47%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
+ Coverage   18.30%   26.78%   +8.47%     
==========================================
  Files          12       12              
  Lines         519      519              
==========================================
+ Hits           95      139      +44     
+ Misses        412      367      -45     
- Partials       12       13       +1     

Impacted Files	Coverage Δ
pkg/collector/networkoutbound_collector.go	91.66% <0.00%> (+91.66%)	⬆️

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