Feeder: prevent resource leak

I confirmed the leak using Valgrind and tested the fix with a simple program using the same workflow as the feeder.
fixes CID 27760 found by Coverity

sched/feeder.cpp

@@ -563,6 +563,7 @@ void feeder_loop() {
     for (int i=0; i<napps; i++) {
         DB_WORK_ITEM* wi = new DB_WORK_ITEM();
         work_items.push_back(*wi);
+        delete wi;
     }
 
     while (1) {