Removed TreeNode's parent reference to avoid maintaning a reference that could keep live big trees (solves #119 and #126)

broker/src/test/java/io/moquette/spi/impl/subscriptions/SubscriptionsStoreTest.java

@@ -404,7 +404,7 @@ public class SubscriptionsStoreTest {
 
     @Test
     public void testRecreatePath_emptyRoot() {
-        TreeNode oldRoot = new TreeNode(null);
+        TreeNode oldRoot = new TreeNode();
         final SubscriptionsStore.NodeCouple resp = store.recreatePath("/finance", oldRoot);
 
         //Verify
@@ -416,7 +416,7 @@ public class SubscriptionsStoreTest {
 
     @Test
     public void testRecreatePath_1layer_tree() {
-        TreeNode oldRoot = new TreeNode(null);
+        TreeNode oldRoot = new TreeNode();
         final SubscriptionsStore.NodeCouple respFinance = store.recreatePath("/finance", oldRoot);
         final SubscriptionsStore.NodeCouple respPlus = store.recreatePath("/+", respFinance.root);
 

broker/src/test/java/io/moquette/spi/impl/subscriptions/TreeNodeTest.java

@@ -13,7 +13,7 @@ public class TreeNodeTest {
 
     @Test
     public void testAddSubscriptionOverwriteAnExistingWithDifferentCleanSessionFlag() throws Exception {
-        TreeNode root = new TreeNode(null);
+        TreeNode root = new TreeNode();
         Subscription existingSub = new Subscription(CLIENT_ID, "/topic", LEAST_ONE, false);
         root.addSubscription(existingSub);
         Set<Subscription> subs = root.findAllByClientID(CLIENT_ID);