Call start() method before FI really executing (#7206)

Author: JackieTien97

server/src/main/java/org/apache/iotdb/db/mpp/execution/fragment/FragmentInstanceContext.java

@@ -70,6 +70,7 @@ public static FragmentInstanceContext createFragmentInstanceContext(
       FragmentInstanceId id, FragmentInstanceStateMachine stateMachine) {
     FragmentInstanceContext instanceContext = new FragmentInstanceContext(id, stateMachine);
     instanceContext.initialize();
+    instanceContext.start();
     return instanceContext;
   }