Construct TestObject in AtomicLinkedListTest via a const reference

Summary:
MSVC doesn't currently guarantee left-to-right argument evaluation order for values constructed via braced initializers, and produces a warning if you try to pass an argument with a non-trivial copy constructor by-value in a constructor used by the braced initializer.
This prevents the warning by simply accepting a const reference instead.

Reviewed By: yfeldblum

Differential Revision: D3705073

fbshipit-source-id: 917ec1bb776d6ec4bfefe50907d4c5ac2f2379b1

folly/test/AtomicLinkedListTest.cpp

@@ -153,7 +153,8 @@ TEST(AtomicIntrusiveLinkedList, Stress) {
 
 class TestObject {
  public:
-  TestObject(size_t id__, std::shared_ptr<void> ptr) : id_(id__), ptr_(ptr) {}
+  TestObject(size_t id__, const std::shared_ptr<void>& ptr)
+      : id_(id__), ptr_(ptr) {}
 
   size_t id() {
     return id_;