Add secret key ref name to username and password env in upload container

[AlexVulaj]

Fixes a bug that was missed in #138 - we weren't using the secret key ref name to properly reference username/password envars in the upload container.

Relevant slack thread: https://redhat-internal.slack.com/archives/C016S65RNG5/p1718723911684519

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 36.78%. Comparing base (44bbf4a) to head (f97aa15).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #140       +/-   ##
===========================================
+ Coverage    7.83%   36.78%   +28.95%     
===========================================
  Files           5        5               
  Lines         383      386        +3     
===========================================
+ Hits           30      142      +112     
+ Misses        350      241      -109     
  Partials        3        3               

Files	Coverage Δ
controllers/mustgather/template.go	87.50% <80.00%> (+87.50%)	⬆️

[mjlshen]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: AlexVulaj, mjlshen

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[openshift-ci]

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