Add handling for "pi.hole.<local_domain>" and "<hostname>.<local_domain>"

[DL6ER]

By submitting this pull request, I confirm the following:

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• I have considered, and confirmed that this submission will be valuable to others.
• I accept that this submission may not be used, and the pull request closed at the will of the maintainer.
• I give this submission freely, and claim no ownership to its content.

How familiar are you with the codebase?:

10

---

#1111 has added special handling for pi.hole and <hostname>. However, we forgot about the case when Pi-hole is the DHCP server and we know the local domain. In this case, we should use the automated reply forming - to serve the most appropriate IP address - also for pi.hole.<local_domain> and <hostname>.<local_domain>.

This PR adds these two new rules and hereby fixes #1168.

[pralor-bot]

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

https://discourse.pi-hole.net/t/issue-with-http-pi-hole-admin-working-but-not-using-the-server-name-horndns-home-instead-of-pi-hole/49847/2

[pralor-bot]

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

https://discourse.pi-hole.net/t/pihole-not-resolving-its-own-hostname/50058/7