delete stronghold mobs form DB when finished

src/engine/gameManager/StrongholdManager.java

@@ -133,6 +133,7 @@ public class StrongholdManager {
         for(Mob mob : mine.strongholdMobs) {
             mob.despawn();
             mob.removeFromCache();
+            DbManager.MobQueries.DELETE_MOB(mob);
         }
 
         //restore the buildings