Remove lua mocks

[ElvinEfendi]

What this PR does / why we need it:
Now the we run tests inside Nginx, we can remove all the now-redundant Lua test mocks and cleanup tests.

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
/assign @antoineco

[codecov-io]

Codecov Report

Merging #2830 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2830   +/-   ##
=======================================
  Coverage   47.33%   47.33%           
=======================================
  Files          75       75           
  Lines        5413     5413           
=======================================
  Hits         2562     2562           
  Misses       2527     2527           
  Partials      324      324

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[antoineco]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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