fix(systemd): add Before=shutdown.target to cloud-init-main.service.tmpl

[aciba90]

Proposed Commit Message

fix(systemd): add Before=shutdown.target to cloud-init-main.service.tmpl

Fixes lintian warning systemd-service-file-shutdown-problems.
See [1, 2].

Remove superflous conditional additions of Conflicts=shutdown.target as
it is unconditionally added for every target.

[1] https://salsa.debian.org/lintian/lintian/-/blob/2.118.0/tags/s/systemd-service-file-shutdown-problems.tag
[2] https://github.com/systemd/systemd/issues/11821

Additional Context

Test Steps

$ DEB_BUILD_OPTIONS=nocheck make deb
$ lintian cloud-init_all.deb 
...
W: cloud-init: systemd-service-file-shutdown-problems [usr/lib/systemd/system/cloud-init-main.service]

Merge type

• Squash merge using "Proposed Commit Message"
• Rebase and merge unique commits. Requires commit messages per-commit each referencing the pull request number (#<PR_NUM>)

[TheRealFalcon]

I think we want the Before alongside the Conflicts. The DefaultDependencies=no means those Conflicts lines aren't implicitly added.

From some random source I found online:

By default, all units and scopes have DefaultDependencies=yes, which implicitly adds Before=shutdown.target and Conflicts=shutdown.target to them. Conflicts means starting shutdown.target stops conflicting units. Starting shutdown.target will stop all conflicting units in parallel (unless otherwise ordered).

[aciba90]

@TheRealFalcon, yes. We need both Before=shutdown.target and Conflicts=shutdown.target present with DefaultDependencies=no. And that is already the case, the Conflicts one is in [1]. I am removing the other Conflicts lines because they are noops, as they apply under certain distros, but [1] add it unconditionally, so they are redundant.

[1] https://github.com/canonical/cloud-init/pull/5653/files#diff-93beecb98a5a39f70a7be0a2928beaee4bc92f85befa463b0bc40a340ff2e1c6R29

[TheRealFalcon]

Ah thanks...sorry, I didn't it on the other line at first.