small fixes for secret hiding CI patches

[roypat]

• workaround for kvm-clock
• correctly clear private flag from free'd folios

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license. For more information on following Developer Certificate of Origin and signing off your commits, please check CONTRIBUTING.md.

PR Checklist

• [ ] I have read and understand CONTRIBUTING.md.
• [ ] I have run tools/devtool checkstyle to verify that the PR passes the automated style checks.
• [ ] I have described what is done in these changes, why they are needed, and how they are solving the problem in a clear and encompassing way.
• [ ] I have updated any relevant documentation (both in code and in the docs) in the PR.
• [ ] I have mentioned all user-facing changes in CHANGELOG.md.
• [ ] If a specific issue led to this PR, this PR closes the issue.
• [ ] When making API changes, I have followed the Runbook for Firecracker API changes.
• [ ] I have tested all new and changed functionalities in unit tests and/or integration tests.
• [ ] I have linked an issue to every new TODO.

---

• [ ] This functionality cannot be added in rust-vmm.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.40%. Comparing base (00ac2f3) to head (650f256).

Files with missing lines	Patch %	Lines
src/vmm/src/builder.rs	0.00%	1 Missing :warning:

Additional details and impacted files

@@                    Coverage Diff                    @@
##           feature/secret-hiding    #5243      +/-   ##
=========================================================
- Coverage                  82.52%   82.40%   -0.12%     
=========================================================
  Files                        250      250              
  Lines                      27386    27384       -2     
=========================================================
- Hits                       22599    22565      -34     
- Misses                      4787     4819      +32     

Flag	Coverage Δ
5.10-c5n.metal	82.77% <0.00%> (-0.14%)	:arrow_down:
5.10-m5n.metal	82.77% <0.00%> (-0.13%)	:arrow_down:
5.10-m6a.metal	82.10% <0.00%> (+<0.01%)	:arrow_up:
5.10-m6g.metal	78.70% <ø> (ø)
5.10-m6i.metal	82.77% <0.00%> (-0.13%)	:arrow_down:
5.10-m7a.metal-48xl	82.08% <0.00%> (ø)
5.10-m7g.metal	78.70% <ø> (ø)
5.10-m7i.metal-24xl	82.72% <0.00%> (-0.14%)	:arrow_down:
5.10-m7i.metal-48xl	82.73% <0.00%> (-0.13%)	:arrow_down:
5.10-m8g.metal-24xl	78.69% <ø> (ø)
5.10-m8g.metal-48xl	78.69% <ø> (ø)
6.1-c5n.metal	82.82% <0.00%> (-0.14%)	:arrow_down:
6.1-m5n.metal	82.82% <0.00%> (-0.14%)	:arrow_down:
6.1-m6a.metal	82.14% <0.00%> (ø)
6.1-m6g.metal	78.70% <ø> (ø)
6.1-m6i.metal	82.81% <0.00%> (-0.14%)	:arrow_down:
6.1-m7a.metal-48xl	82.13% <0.00%> (ø)
6.1-m7g.metal	78.70% <ø> (ø)
6.1-m7i.metal-24xl	82.83% <0.00%> (-0.14%)	:arrow_down:
6.1-m7i.metal-48xl	82.83% <0.00%> (-0.13%)	:arrow_down:
6.1-m8g.metal-24xl	78.69% <ø> (ø)
6.1-m8g.metal-48xl	78.69% <ø> (ø)
6.14-c5n.metal	82.79% <0.00%> (-0.13%)	:arrow_down:
6.14-m5n.metal	82.79% <0.00%> (-0.14%)	:arrow_down:
6.14-m6a.metal	82.11% <0.00%> (ø)
6.14-m6g.metal	78.65% <ø> (ø)
6.14-m6i.metal	82.78% <0.00%> (-0.14%)	:arrow_down:
6.14-m7a.metal-48xl	82.10% <0.00%> (ø)
6.14-m7g.metal	78.65% <ø> (-0.01%)	:arrow_down:
6.14-m7i.metal-24xl	82.79% <0.00%> (-0.14%)	:arrow_down:
6.14-m7i.metal-48xl	82.79% <0.00%> (-0.14%)	:arrow_down:
6.14-m8g.metal-24xl	78.64% <ø> (-0.01%)	:arrow_down:
6.14-m8g.metal-48xl	78.64% <ø> (-0.01%)	:arrow_down:

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