Security: Disallow SSDP device discovery from non-local addresses.

Protection against MythTV's use in SSDP Reflection attacks.

https://www.prolexic.com/knowledge-center-ddos-threat-advisory-ssdp-reflection-ddos-attacks.html
https://www.prolexic.com/kcresources/prolexic-threat-advisories/prolexic-threat-advisory-ssdp-reflection-ddos-attacks/ssdp-reflection-attacks-cybersecurity-locked.html

No CVE assigned yet.

(cherry picked from commit 52cb0b5679a5b20a55ba5cbe6b1064b72c66576f)