Update entity target data to reflect current AI status. Fixes BUKKIT-2280

The new AI system introduced by Minecraft 1.2 no longer relies on the
target field in the entity so it is frequently out of sync with what the
entity is actually doing. This modifies the AI goal to update the target
so our API can return the correct information.

src/main/java/net/minecraft/server/PathfinderGoalTarget.java

@@ -119,10 +119,12 @@ public abstract class PathfinderGoalTarget extends PathfinderGoal {
 
                     org.bukkit.event.entity.EntityTargetLivingEntityEvent event = org.bukkit.craftbukkit.event.CraftEventFactory.callEntityTargetLivingEvent(this.d, entityliving, reason);
                     if (event.isCancelled() || event.getTarget() == null) {
+                        if (this.d instanceof EntityCreature) ((EntityCreature) this.d).target = null;
                         return false;
                     } else if (entityliving.getBukkitEntity() != event.getTarget()) {
                         this.d.b((EntityLiving) ((org.bukkit.craftbukkit.entity.CraftEntity) event.getTarget()).getHandle());
                     }
+                    if (this.d instanceof EntityCreature) ((EntityCreature) this.d).target = ((org.bukkit.craftbukkit.entity.CraftEntity) event.getTarget()).getHandle();
                     // CraftBukkit end
 
                     return true;