more meaningful assertion for tls hsts test

[ElvinEfendi]

What this PR does / why we need it:

e2e tests should be concerned about end result not how the result is achieved. I've also tightened the assertion by using Equal instead of Contains.

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:

[codecov-io]

Codecov Report

Merging #4597 into master will increase coverage by 1.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4597      +/-   ##
==========================================
+ Coverage   58.58%   59.65%   +1.06%     
==========================================
  Files          88       88              
  Lines        6735     6937     +202     
==========================================
+ Hits         3946     4138     +192     
+ Misses       2352     2348       -4     
- Partials      437      451      +14

Impacted Files	Coverage Δ
internal/ingress/controller/template/template.go	82.87% <0%> (+3.71%)	⬆️

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[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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