DB/Gameobject: Everfrost Chip

Additional spawns of http://www.wowhead.com/object=193997 Everfrost Chip on top of the 2 already in db.
forgot to copy and paste line to set guid
Scripts/Ulduar: Exclude Ignis' main target from the Slag Pot target selector

Closes #10516
Scripts/ScarletMonastery: Summon the Headless Horseman once the Call the Headless Horseman is quest complete

By @cr4st
Closes #13273