Fix multiple restarts while importing with Teleporter

[yubiuser]

What does this PR aim to accomplish?:

Do not restart FTL for each local DNS record or local CNAME record. This was partly fixed by #1925 but re-introduced with #2410.

Background: we use addCustomDNSEntry and addCustomCNAMEEntry when adding domains through the web interface but also via Teleporter. We don't want a reload for each added item, but a restart when added via web but not via Teleporter. Teleporter is handling restarts by itself because it only restarts when everything is imported.

So far, this bug was hiding, but with adding a native systemd unit and setting a start limit of 5 within 60 seconds this unveiled the bug.

https://github.com/pi-hole/pi-hole/blob/c7ad7113d70f63b0b4a5460daaf5ada8f10c28f4/advanced/Templates/pihole-FTL.systemd#L14-L16

How does this PR accomplish the above?:

Adds a new variable $teleporter to the function to signal if it was called from teleporter.php.

---

By submitting this pull request, I confirm the following:

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 and I have tested my changes.
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)
6. I have checked that another pull request for this purpose does not exist.
7. I have considered, and confirmed that this submission will be valuable to others.
8. I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
9. I give this submission freely, and claim no ownership to its content.

---

• I have read the above and my PR is ready for review. Check this box to confirm

[pralor-bot]

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

https://discourse.pi-hole.net/t/pi-hole-ftl-v5-21-web-v5-18-4-and-core-v5-15-4-released/61096/1