Core/Spells: Fix summon position of Argent Valiant

Ref #8718

sql/updates/world/2015_05_19_02_world.sql

@@ -0,0 +1,3 @@
+DELETE FROM `spell_target_position` WHERE `id`=63171;
+INSERT INTO `spell_target_position` (`id`, `effIndex`, `target_map`, `target_position_x`, `target_position_y`, `target_position_z`, `target_orientation`) VALUES 
+(63171, 0, 571, 8533.11, 1069.66, 551.784, 0.5296);