Fix folly/io/async/test:async_test - AsyncSocketTest.ConnectionExpiry

Summary: The worker thread just needed to be killed before the `AcceptCallback`. `AsyncServerSocket` calls a method on this callback class in its dtor, so it must either be alive or removed using `removeAcceptCallback`.

Differential Revision: D24972293

fbshipit-source-id: 2c7b6d64c2b9b8c00d03107002fa31e565df2a01

folly/io/async/test/AsyncSocketTest2.cpp

@@ -4210,7 +4210,6 @@ TEST(AsyncSocketTest, ConnectionExpiry) {
   constexpr auto kConnectionExpiryDuration = milliseconds(10);
   serverSocket->setQueueTimeout(kConnectionExpiryDuration);
 
-  ScopedEventBaseThread acceptThread("ioworker_test");
   TestAcceptCallback acceptCb;
   acceptCb.setConnectionAcceptedFn(
       [&, called = false](auto&&...) mutable {
@@ -4230,6 +4229,7 @@ TEST(AsyncSocketTest, ConnectionExpiry) {
         // second message expires before it has a chance to dequeue.
         std::this_thread::sleep_for(kConnectionExpiryDuration);
       });
+  ScopedEventBaseThread acceptThread("ioworker_test");
 
   TestConnectionEventCallback connectionEventCb;
   serverSocket->setConnectionEventCallback(&connectionEventCb);