make sure ingress-nginx instances are watching their namespace only during test runs

[ElvinEfendi]

What this PR does / why we need it:

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:

[ElvinEfendi]

/assign @aledbf

[aledbf]

/approve
/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[codecov-io]

Codecov Report

Merging #2577 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2577   +/-   ##
=======================================
  Coverage   40.54%   40.54%           
=======================================
  Files          75       75           
  Lines        5105     5105           
=======================================
  Hits         2070     2070           
  Misses       2754     2754           
  Partials      281      281

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