Update maxhealth for entities that have variable max health. Fixes BUKKIT-3308

Slimes and wolves have health that can change based on certain
conditions. So we check if their max health should be updated, and if
it has been customized in any way.

We also scale the wolf's health for their tail

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

@@ -26,10 +26,16 @@ public class EntitySlime extends EntityLiving implements IMonster {
 
     // CraftBukkit - protected -> public
     public void setSize(int i) {
+        boolean updateMaxHealth = this.getMaxHealth() == this.maxHealth; // CraftBukkit
         this.datawatcher.watch(16, new Byte((byte) i));
         this.a(0.6F * (float) i, 0.6F * (float) i);
         this.setPosition(this.locX, this.locY, this.locZ);
-        this.setHealth(this.getMaxHealth());
+        // CraftBukkit start
+        if (updateMaxHealth) {
+            this.maxHealth = this.getMaxHealth();
+        }
+        this.setHealth(this.maxHealth);
+        // CraftBukkit end
         this.bd = i;
     }