HugeGraph-1324: fix "Assertion error: (is_last_reference)"

Change-Id: Ie9f9679f87ac7967de54184191a9e6d29130b32f

hugegraph-core/src/main/java/com/baidu/hugegraph/backend/serializer/BinaryEntryIterator.java

@@ -91,6 +91,7 @@ public class BinaryEntryIterator<Elem> extends BackendEntryIterator {
                 if (this.query.paging() && this.results.hasNext()) {
                     this.results.next();
                 }
+                this.results.close();
                 break;
             }
         }

hugegraph-core/src/main/java/com/baidu/hugegraph/task/HugeTaskScheduler.java

@@ -105,7 +105,7 @@ public class HugeTaskScheduler {
     public <V> Future<?> restore(HugeTask<V> task) {
         E.checkArgumentNotNull(task, "Task can't be null");
         task.status(HugeTaskStatus.RESTORING);
-        return this.submit(task);
+        return this.submitTask(task);
     }
 
     public <V> Future<?> schedule(HugeTask<V> task) {

hugegraph-core/src/main/java/com/baidu/hugegraph/task/HugeTaskStatus.java

@@ -27,7 +27,7 @@ public enum HugeTaskStatus implements SerialEnum {
 
     NEW(1, "new"),
     QUEUED(2, "queued"),
-    RESTORING(4, "restoring"),
+    RESTORING(3, "restoring"),
     RUNNING(4, "running"),
     SUCCESS(5, "success"),
     CANCELLED(6, "cancelled"),

hugegraph-example/src/main/java/com/baidu/hugegraph/example/Example1.java

@@ -429,6 +429,7 @@ public class Example1 {
         variables.set("time", 3);
         variables.set("owner", "zhangyi1");
         variables.keys();
+        graph.tx().commit();
         variables.remove("time");
         variables.get("time");
         variables.get("owner");

hugegraph-rocksdb/src/main/java/com/baidu/hugegraph/backend/store/rocksdb/RocksDBStdSessions.java

@@ -649,7 +649,13 @@ public class RocksDBStdSessions extends RocksDBSessions {
 
         @Override
         public boolean hasNext() {
-            this.matched = this.itor.isOwningHandle() && this.itor.isValid();
+            this.matched = this.itor.isOwningHandle();
+            if (!this.matched) {
+                // Maybe closed
+                return this.matched;
+            }
+
+            this.matched = this.itor.isValid();
             if (this.matched) {
                 // Update position for paging
                 this.position = this.itor.key();