[release-1.11] Set correct fqdn on private cluster

[mihaiandreiratoiu]

What type of PR is this?
Adapted from #4225
/kind bug

What this PR does / why we need it:
On private cluster with the managedcontrolplane

• EnablePrivateCluster: true
• EnablePrivateClusterPublicFQDN: false
  The fqdn property is not available. The cluster defaults to the privateFQDN
  The Cluster resource remains in provisioning state due to the capz error

spec.controlPlaneEndpoint.host: Required value" "AzureManagedCluster"

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

 Fix: Set correct host on private cluster with public fqdn disabled

[k8s-ci-robot]

Hi @mihaiandreiratoiu. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[nojnhuh]

/ok-to-test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (3a1b5bf) 56.69% compared to head (de721bb) 56.70%.
Report is 3 commits behind head on release-1.11.

Additional details and impacted files

@@              Coverage Diff              @@
##           release-1.11    #4242   +/-   ##
=============================================
  Coverage         56.69%   56.70%           
=============================================
  Files               187      187           
  Lines             19214    19222    +8     
=============================================
+ Hits              10893    10899    +6     
- Misses             7691     7693    +2     
  Partials            630      630           

Files	Coverage Δ
azure/services/managedclusters/managedclusters.go	77.77% <100.00%> (+2.43%)	⬆️

... and 1 file with indirect coverage changes

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[nojnhuh]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nojnhuh

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[k8s-ci-robot]

LGTM label has been added.

Git tree hash: a855193433db6baa8d9a411da42b285eaf36b85f