Added 'cleanup()' method to clear the node list at the end of the operations.

Signed-off-by: Cristiano Urban <cristiano.urban@inaf.it>

transfer_service/retrieve_preprocessor.py

@@ -30,6 +30,9 @@ class RetrievePreprocessor(TaskExecutor):
             self.nodeList = self.dbConn.getVOSpacePathList(vospacePath)
         self.jobObj.jobInfo["nodeList"] = self.nodeList        
 
+    def cleanup(self):
+        self.nodeList.clear()
+
     def run(self):
         print("Starting retrieve preprocessor...")
         self.setSourceQueueName("read_pending")
@@ -41,4 +44,5 @@ class RetrievePreprocessor(TaskExecutor):
                 self.execute()
                 self.destQueue.insertJob(self.jobObj)
                 self.srcQueue.extractJob()
+                self.cleanup()
                 print(f"Job {self.jobObj.jobId} MOVED from {self.srcQueue.name()} to {self.destQueue.name()}")