Fix pessimizing move warning being emitted by the compiler

indra/llcommon/llthreadsafequeue.h

@@ -452,7 +452,9 @@ ElementT LLThreadSafeQueue<ElementT, QueueT>::pop(void)
         // so we can finish draining the queue.
         pop_result popped = pop_(lock1, value);
         if (popped == POPPED)
-            return std::move(value);
+            // don't use std::move when returning local value because
+            // it prevents the compiler from optimizing with copy elision
+            return value;
 
         // Once the queue is DONE, there will never be any more coming.
         if (popped == DONE)