Transition KVM disk-only VM snapshot to Error state on delete failure

[DaanHoogland]

deleteVMSnapshot in KvmFileBasedStorageVmSnapshotStrategy transitioned the snapshot to Expunging but had no exception handling, so any exception thrown by the merge/delete helpers (e.g. an agent command timeout) left the snapshot permanently stuck in Expunging. VMSnapshotManagerImpl.hasActiveVMSnapshotTasks treats Expunging as active work, so this permanently blocked reboot and further snapshot operations on the VM.

Wrap the delete body in a try/catch, mirroring the existing pattern already used by takeVMSnapshot and revertVMSnapshot in the same class: on any RuntimeException, transition the snapshot to Error via the existing Expunging -> OperationFailed state machine transition before rethrowing.

Test: KvmFileBasedStorageVmSnapshotStrategyTest#testDeleteVMSnapshotMarksSnapshotFailedWhenDeleteThrowsAfterExpungeRequested fails without this fix (no OperationFailed transition is ever fired) and passes with it.

Description

This PR...

Fixes: #14019

Types of changes

• Breaking change (fix or feature that would cause existing functionality to change)
• New feature (non-breaking change which adds functionality)
• 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

Feature/Enhancement Scale

• Major
• Minor

Bug Severity

• BLOCKER
• Critical
• Major
• Minor
• Trivial

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How Has This Been Tested?

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[codecov]

Codecov Report

❌ Patch coverage is 10.81081% with 33 lines in your changes missing coverage. Please review.
✅ Project coverage is 18.00%. Comparing base (250695e) to head (678ed74).
⚠️ Report is 3 commits behind head on 4.22.

Files with missing lines	Patch %	Lines
...napshot/KvmFileBasedStorageVmSnapshotStrategy.java	10.81%	33 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               4.22   #14283      +/-   ##
============================================
- Coverage     18.00%   18.00%   -0.01%     
+ Complexity    16220    16218       -2     
============================================
  Files          5936     5936              
  Lines        535716   535720       +4     
  Branches      65596    65596              
============================================
- Hits          96457    96439      -18     
- Misses       428269   428294      +25     
+ Partials      10990    10987       -3     

Flag	Coverage Δ
uitests	4.02% <ø> (ø)
unittests	19.07% <10.81%> (-0.01%)	⬇️

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