[LP#2143365] When containerd is installed by resource, don't restart service with apt

[addyess]

Bug fix LP#2143365

#84 introduced a change where containerd is apt install even if the bin is replaced using a charm resource. That's fine, but the charm shouldn't restart containerd when its resource managed.

This change prevents service restarts of containerd when the binary is resource managed.

[Copilot]

Pull request overview

Fixes LP#2143365 by preventing containerd service restarts triggered by apt when containerd is resource-managed (e.g., during upgrade-charm), while still allowing apt reinstall to refresh systemd units/configs/deps.

Changes:

• Update upgrade_charm() to reinstall containerd packages without restarting services when a containerd resource is installed.
• Add _apt_restart_services() context manager to control apt/needrestart behavior during apt_install.
• Add unit test coverage for _apt_restart_services() and remove stray whitespace in test files.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/reactive/containerd.py	Adds restart-suppression context manager and uses it to avoid restarts during resource-managed upgrade-charm reinstalls.
tests/unit/test_containerd_reactive.py	Adds parametrized unit tests for the new context manager behavior.
tests/unit/conftest.py	Removes stray whitespace.
tests/integration/test_containerd_integration.py	Removes stray whitespace.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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