Core/Creature: Initialize the creature's default movement generator on respawn.

Fixes creatures which are moving by default, but not continuing it after respawning.

--HG--
branch : trunk

src/server/game/Entities/Creature/Creature.cpp

@@ -1601,6 +1601,8 @@ void Creature::Respawn(bool force)
             SetByteValue(UNIT_FIELD_BYTES_0, 2, minfo->gender);
         }
 
+        GetMotionMaster()->InitDefault();
+
         //Call AI respawn virtual function
         if (IsAIEnabled)
             AI()->JustRespawned();