[Release-1.29] Fix external etcd connection

[vitorsavian]

• Issue [Release-1.29] - RKE2 --datastore-endpoint for etcd not working #6455
• Backport from Fix external etcd connection #6355

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 25.89%. Comparing base (1ec1285) to head (0cb49c6).

Files	Patch %	Lines
pkg/rke2/rke2_linux.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.29    #6464      +/-   ##
================================================
+ Coverage         25.87%   25.89%   +0.01%     
================================================
  Files                32       32              
  Lines              2736     2738       +2     
================================================
+ Hits                708      709       +1     
- Misses             1981     1983       +2     
+ Partials             47       46       -1     

Flag	Coverage Δ
inttests	9.75% <0.00%> (-0.01%)	⬇️
unittests	18.40% <0.00%> (+0.02%)	⬆️

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