Ensure we also change ownership of the WAL database files

[DL6ER]

What does this implement/fix?

If FTL is being invoked in an unusual way, it can happen that the database is created as root and later re-owned to a low-privilege user. Since the default database mode is now WAL, we have additional -shm and -wal files which need to be re-owned as well or the database becomes read-only.

This permission issue "auto-fixes" on the next FTL restart and everything will be fine thereafter. Nonetheless, this PR ensures the permissions are already correct during the initial start and not only after the first restart.

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Related issue or feature (if applicable): See linked Discourse thread below.

Pull request in docs with documentation (if applicable): N/A

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1. I have read and understood the contributors guide, as well as this entire template. I understand which branch to base my commits and Pull Requests against.
2. I have commented my proposed changes within the code.
3. I am willing to help maintain this change if there are issues with it later.
4. It is compatible with the EUPL 1.2 license
5. I have squashed any insignificant commits. (git rebase)

Checklist:

• [x] The code change is tested and works locally.
• [x] I based my code and PRs against the repositories developmental branch.
• [x] I signed off all commits. Pi-hole enforces the DCO for all contributions
• [x] I signed all my commits. Pi-hole requires signatures to verify authorship
• [x] I have read the above and my PR is ready for review.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/usage-of-dnsmasqs-user-option-does-not-chown-db-shm-and-db-wal-files-on-first-launch/70244/3

[DL6ER]

Confirmed working by OP on Discourse