[release-1.28] Fix agent supervisor port using apiserver port instead

[brandond]

Proposed Changes

Fix agent supervisor port using apiserver port instead

The agent's supervisor listener on RKE2 is using the wrong port. Didn't notice it here because they're the same in k3s.

Types of Changes

bugfix

Verification

Can only be tested in RKE2

Testing

Linked Issues

• [Release-1.28] - Expose RKE2 metrics via supervisor port rancher/rke2#6091 (comment)

User-Facing Change

NONE

Further Comments

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 35.89%. Comparing base (b261f29) to head (76a5268).
Report is 1 commits behind head on release-1.28.

Files	Patch %	Lines
pkg/agent/https/https.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.28   #10355      +/-   ##
================================================
- Coverage         36.09%   35.89%   -0.20%     
================================================
  Files               163      160       -3     
  Lines             16644    14057    -2587     
================================================
- Hits               6007     5046     -961     
+ Misses             9621     8015    -1606     
+ Partials           1016      996      -20     

Flag	Coverage Δ
e2etests	35.89% <50.00%> (-0.38%)	⬇️
unittests	?

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