Scripts/ScarletEnclave: Fix uninitialized values in Highlord Darion Mograine

Reset() has if checks on values that are initialized after them so it's required to initialize these fields in the constructor.

Valgrind log:
 Conditional jump or move depends on uninitialised value(s)
  by 0x11CF472: HashMapHolder<Creature>::Find(unsigned long) (ObjectAccessor.h:67)
  by 0x11CE36F: Creature* ObjectAccessor::GetObjectInWorld<Creature>(unsigned long, Creature*) (ObjectAccessor.h:114)
  by 0x1257C13: Creature* ObjectAccessor::GetObjectInMap<Creature>(unsigned long, Map*, Creature*) (ObjectAccessor.h:135)
  by 0x12E64F1: Map::GetCreature(unsigned long) (Map.cpp:2767)
  by 0x10AF4DE: Unit::GetCreature(WorldObject&, unsigned long) (Unit.cpp:13021)
  by 0x16F8F81: npc_highlord_darion_mograine::npc_highlord_darion_mograineAI::Reset() (chapter5.cpp:386)
  by 0x16F8D36: npc_highlord_darion_mograine::npc_highlord_darion_mograineAI::npc_highlord_darion_mograineAI(Creature*) (chapter5.cpp:314)
  by 0x16F8CD6: npc_highlord_darion_mograine::GetAI(Creature*) const (chapter5.cpp:307)
  by 0x132AF6C: ScriptMgr::GetCreatureAI(Creature*) (ScriptMgr.cpp:796)
  by 0x1441D45: FactorySelector::selectAI(Creature*) (CreatureAISelector.cpp:41)
DB/SAI: Eyes of Grillok

By @dr-j fixes #10909
Merge branch 'master' of git://github.com/TrinityCore/TrinityCore