Rework max health values. Fixes BUKKIT-4398

By: Wesley Wolfe <weswolf@aol.com>

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftLivingEntity.java

@@ -19,6 +19,7 @@ import net.minecraft.server.EntitySnowball;
 import net.minecraft.server.EntityPlayer;
 import net.minecraft.server.EntityPotion;
 import net.minecraft.server.EntityWitherSkull;
+import net.minecraft.server.GenericAttributes;
 import net.minecraft.server.MobEffect;
 import net.minecraft.server.MobEffectList;
 import net.minecraft.server.Packet42RemoveMobEffect;
@@ -83,13 +84,13 @@ public class CraftLivingEntity extends CraftEntity implements LivingEntity {
     }
 
     public double getMaxHealth() {
-        return getHandle().maxHealth;
+        return getHandle().getMaxHealth();
     }
 
     public void setMaxHealth(double amount) {
         Validate.isTrue(amount > 0, "Max health must be greater than 0");
 
-        getHandle().maxHealth = (float) amount;
+        getHandle().a(GenericAttributes.a).a(amount);
 
         if (getHealth() > amount) {
             setHealth(amount);