synchronize start and stop methods for datasetlifecyclemanager
diff --git a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
index 7232f01..df2fd61 100644
--- a/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
+++ b/asterix-common/src/main/java/edu/uci/ics/asterix/common/context/DatasetLifecycleManager.java
@@ -338,11 +338,11 @@
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
     }
 
     @Override
-    public void stop(boolean dumpState, OutputStream outputStream) throws IOException {
+    public synchronized void stop(boolean dumpState, OutputStream outputStream) throws IOException {
         if (dumpState) {
             dumpState(outputStream);
         }