Make the exception message with the instance id which will help us to find the bug. (#1005)

Fixed #999

apm-collector/apm-collector-storage/collector-storage-es-provider/src/main/java/org/apache/skywalking/apm/collector/storage/es/dao/InstanceHeartBeatEsPersistenceDAO.java

@@ -61,7 +61,7 @@ public class InstanceHeartBeatEsPersistenceDAO extends EsDAO implements IInstanc
     }
 
     @Override public IndexRequestBuilder prepareBatchInsert(Instance data) {
-        throw new UnexpectedException("There is no need to merge stream data with database data.");
+        throw new UnexpectedException("Received an instance heart beat message under instance id= " + data.getId() + " , which doesn't exist.");
     }
 
     @Override public UpdateRequestBuilder prepareBatchUpdate(Instance data) {