more dev-env script improvements

[ElvinEfendi]

What this PR does / why we need it:
Remove unused flags and commands and make the script actually work.

Tested with kubectl v1.14.2.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #

Special notes for your reviewer:

[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, ElvinEfendi

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• OWNERS [ElvinEfendi,aledbf]

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[aledbf]

/test pull-ingress-nginx-test

[codecov-io]

Codecov Report

Merging #4415 into master will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4415      +/-   ##
==========================================
+ Coverage   58.63%   58.68%   +0.04%     
==========================================
  Files          88       88              
  Lines        6569     6569              
==========================================
+ Hits         3852     3855       +3     
+ Misses       2288     2285       -3     
  Partials      429      429

Impacted Files	Coverage Δ
internal/ingress/metric/collectors/process.go	90.42% <0%> (+2.12%)	⬆️
internal/watch/file_watcher.go	84.61% <0%> (+3.84%)	⬆️

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