Avoid SEGFAULT when cleaning up installation in integration tests fixture

[pchila]

What does this PR do?

Fix a SIGSEGV when cleaning up agent installed using fixture functionality

Why is it important?

Integration tests fail during cleanup phase and pollute the test output

Checklist

• My code follows the style guidelines of this project
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have made corresponding change to the default configuration files
  - [ ] I have added tests that prove my fix is effective or that my feature works
  - [ ] I have added an entry in ./changelog/fragments using the changelog tool
  - [ ] I have added an integration test or an E2E test

Author's Checklist

• [ ]

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• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

[mergify]

This pull request does not have a backport label. Could you fix it @pchila? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[elasticmachine]

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• Start Time: 2023-05-29T13:20:28.468+0000

• Duration: 21 min 51 sec

Test stats 🧪

Test	Results
Failed	0
Passed	5663
Skipped	19
Total	5682

💚 Flaky test report

Tests succeeded.

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	98.611% (71/72)	👍
Files	68.273% (170/249)	👍
Classes	67.021% (315/470)	👍
Methods	53.678% (956/1781)	👍
Lines	39.513% (11013/27872)	👎 -0.002
Conditionals	100.0% (0/0)	💚