snapshot: fix listSnapshots when storage pool is removed

[yadvr]

This fixes the case when the storage pool is removed as well the KVM host and the subsequent volumes on the host. When that happened, listing snapshots (for recovery purposes) cause NPE as the pool_id was null, but last_pool_id for the related destroyed volume wasn't null. This adds a fallback logic.

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

Screenshots (if appropriate):

How Has This Been Tested?

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

[yadvr]

@blueorangutan package

[blueorangutan]

@yadvr 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.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 17.59%. Comparing base (71f47d6) to head (aa1893b).
⚠️ Report is 92 commits behind head on 4.22.

Files with missing lines	Patch %	Lines
...torage/snapshot/StorageSystemSnapshotStrategy.java	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               4.22   #12433      +/-   ##
============================================
+ Coverage     17.56%   17.59%   +0.02%     
- Complexity    15545    15601      +56     
============================================
  Files          5909     5910       +1     
  Lines        529056   529780     +724     
  Branches      64617    64730     +113     
============================================
+ Hits          92953    93224     +271     
- Misses       425648   426061     +413     
- Partials      10455    10495      +40     

Flag	Coverage Δ
uitests	3.60% <ø> (+0.01%)	⬆️
unittests	18.66% <0.00%> (+0.02%)	⬆️

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[DaanHoogland]

lgtm, (no doubt even more fallback can be added..?? i.e. volumeStoragePoolId == null than throw a suitable CloudRuntimeException)

[sureshanaparti]

clgtm

[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 16382

[yadvr]

@blueorangutan test