Update dns policy for sandbox buildkit instance to ClusterFirstWithHo…

[jeevb]

…stNet

Why are the changes needed?

Buildkitd instance currently cannot resolve in-cluster DNS entries such as https://flyte-sandbox-minio.flyte:9000. This change fixes it.

How was this patch tested?

• Ensured that local build/push via image spec is working as intended.
• Ensured that in-cluster DNS entries can be resolved from within the buildkitd instance.

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Related PRs

Docs link

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (a726c36) 58.11% compared to head (77cde4c) 58.12%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4678   +/-   ##
=======================================
  Coverage   58.11%   58.12%           
=======================================
  Files         626      626           
  Lines       53815    53815           
=======================================
+ Hits        31275    31278    +3     
+ Misses      20039    20035    -4     
- Partials     2501     2502    +1     

Flag	Coverage Δ
unittests	58.12% <ø> (+<0.01%)	⬆️

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