fix install location of systemd drop-in configs

[nmeyerhans]

Fixes #5613

Proposed Commit Message

<fix>(systemd) Correct location of installed drop-in files

As noted in the systemd documentation, /etc is reserved for "System
units created by the administrator" while the lib directory should be
used by "System units installed by the distribution package manager".

Fixes GH-5613

Additional Context

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1078180
https://manpages.debian.org/bookworm/systemd/systemd.unit.5.en.html

Test Steps

Validate that cloud-init installations currently include /etc/systemd/system/[email protected]/disable-sshd-keygen-if-cloud-init-active.conf. After this change, the file is installed as /usr/lib/systemd/system/[email protected]/disable-sshd-keygen-if-cloud-init-active.conf

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]

LGTM! Thanks!