UPT: Add variable to define custom sampler host and port

[reynaldiwijaya]

What this PR does / why we need it:
This PR will accommodate custom Jaeger Sampler Remote Host and Remote Port. In many cases we want a centralize sampler configuration (in collector). The current implementation of nginx ingress will only use localhost jaeger agent for this purpose. The url given does not include /sampling as well, which is not going to work if it is not included

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #
fixes #3894

Special notes for your reviewer:
Some documentation in pull request is not updated, e.g. make verify is no longer exist in Makefile

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[aledbf]

/ok-to-test

[aledbf]

@reynaldiwijaya please update the configmap configuration. If you do that this LGTM

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@ff80dca). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff            @@
##             master   #4105   +/-   ##
========================================
  Coverage          ?   57.7%           
========================================
  Files             ?      87           
  Lines             ?    6452           
  Branches          ?       0           
========================================
  Hits              ?    3723           
  Misses            ?    2298           
  Partials          ?     431

Impacted Files	Coverage Δ
internal/ingress/controller/nginx.go	29% <ø> (ø)
internal/ingress/controller/config/config.go	98.56% <100%> (ø)

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[reynaldiwijaya]

@aledbf I only found documentation for anything related to configmap (docs/user-guide/nginx-configuration/configmap.md). If this is the file that you meant, I have updated it. If it is not the one, please let me know, i will update accordingly

[aledbf]

/lgtm
/approve

[aledbf]

@reynaldiwijaya thanks!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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