nasbackup: fix agent.log is cleaned when backup stopped vm

[weizhouapache]

Description

This PR fixes the issue that when backing up a stopped vm, agent.log is cleaned up and all previous logs disappear.

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?

[Copilot]

Pull request overview

This PR fixes unintended truncation of the KVM agent log during NAS backups of stopped VMs by changing the qemu-img convert logging redirection to append rather than overwrite /var/log/cloudstack/agent/agent.log.

Changes:

• Append qemu-img convert stdout to the agent log (>>) in the stopped-VM backup path to prevent log loss.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 19.64%. Comparing base (75748a5) to head (94b3675).

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #13641      +/-   ##
============================================
- Coverage     19.65%   19.64%   -0.01%     
  Complexity    19792    19792              
============================================
  Files          6368     6368              
  Lines        575107   575107              
  Branches      70370    70370              
============================================
- Hits         113016   113008       -8     
- Misses       449808   449813       +5     
- Partials      12283    12286       +3     

Flag	Coverage Δ
uitests	3.41% <ø> (ø)
unittests	20.92% <ø> (-0.01%)	⬇️

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[weizhouapache]

@blueorangutan package

[blueorangutan]

@weizhouapache a [SL] Jenkins job has been kicked to build packages. It will be bundled with no SystemVM templates. I'll keep you posted as I make progress.

[blueorangutan]

Packaging result [SF]: ✔️ el8 ✔️ el9 ✔️ el10 ✔️ debian ✔️ suse15. SL-JID 18603

[winterhazel]

Looks good (did not test).