CKS: Use Zone MTUs when network is created at the time of CKS cluster creation

[Pearl1594]

Description

This PR fixes: #12205 When a cluster is created without specifying a network, then an isolated network is created automatically with the default MTU. However, if there is an MTU set at zone level, then it would be ideal to use that instead.

Types of changes

• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] New feature (non-breaking change which adds functionality)
• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] Enhancement (improves an existing feature and functionality)
• [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
• [ ] Build/CI
• [ ] Test (unit or integration test code)

Feature/Enhancement Scale or Bug Severity

Bug Severity

• [ ] BLOCKER
• [ ] Critical
• [ ] Major
• [X] Minor
• [ ] Trivial

Screenshots (if appropriate):

How Has This Been Tested?

How did you try to break this feature and the system with this change?

[codecov[bot]]

Codecov Report

:x: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 16.21%. Comparing base (4348386) to head (a3cba04). :warning: Report is 3 commits behind head on 4.20.

Files with missing lines	Patch %	Lines
...bernetes/cluster/KubernetesClusterManagerImpl.java	0.00%	4 Missing :warning:
...ain/java/com/cloud/network/NetworkServiceImpl.java	0.00%	4 Missing :warning:

Additional details and impacted files

@@            Coverage Diff            @@
##               4.20   #12228   +/-   ##
=========================================
  Coverage     16.21%   16.21%           
- Complexity    13353    13354    +1     
=========================================
  Files          5657     5657           
  Lines        498647   498654    +7     
  Branches      60533    60533           
=========================================
+ Hits          80863    80869    +6     
+ Misses       408771   408766    -5     
- Partials       9013     9019    +6     

Flag	Coverage Δ
uitests	4.00% <ø> (ø)
unittests	17.07% <0.00%> (+<0.01%)	:arrow_up:

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[Pearl1594]

@blueorangutan package

[blueorangutan]

@Pearl1594 a [SL] Jenkins job has been kicked to build packages. It will be bundled with KVM, XenServer and VMware SystemVM templates. I'll keep you posted as I make progress.

[sonarqubecloud[bot]]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 40%)

See analysis details on SonarQube Cloud

[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 15979