Make ChangeStreamBatchCursor#close idempotent

JAVA-3442

Author: jyemin

driver-core/src/main/com/mongodb/operation/ChangeStreamBatchCursor.java

@@ -40,6 +40,7 @@ final class ChangeStreamBatchCursor<T> implements AggregateResponseBatchCursor<T
 
     private AggregateResponseBatchCursor<RawBsonDocument> wrapped;
     private BsonDocument resumeToken;
+    private volatile boolean closed;
 
     ChangeStreamBatchCursor(final ChangeStreamOperation<T> changeStreamOperation,
                             final AggregateResponseBatchCursor<RawBsonDocument> wrapped,
@@ -91,8 +92,11 @@ public List<T> apply(final AggregateResponseBatchCursor<RawBsonDocument> queryBa
 
     @Override
     public void close() {
-        wrapped.close();
-        binding.release();
+        if (!closed) {
+            closed = true;
+            wrapped.close();
+            binding.release();
+        }
     }
 
     @Override

driver-core/src/test/unit/com/mongodb/operation/ChangeStreamBatchCursorSpecification.groovy

@@ -57,6 +57,12 @@ class ChangeStreamBatchCursorSpecification extends Specification {
 
         then:
         1 * wrapped.close()
+
+        when:
+        cursor.close()
+
+        then:
+        0 * wrapped.close()
     }
 
 }