modernize Future::get(): 4/n = codemod to std::move for non-ptr exprs

Summary:
Codemod non-pointer expressions:
   - expr.get() ==> std::move(expr).get()
   - expr.get(dur) ==> std::move(expr).get(dur)
when expr is not already an xvalue.

Reviewed By: yfeldblum

Differential Revision: D8430137

fbshipit-source-id: 20da463f9cceb5cb1e71a7226f3b11d1e8007011

folly/fibers/test/FibersTest.cpp

@@ -1494,8 +1494,8 @@ TEST(FiberManager, remoteFutureTest) {
   auto f1 = fiberManager.addTaskFuture([&]() { return testValue1; });
   auto f2 = fiberManager.addTaskRemoteFuture([&]() { return testValue2; });
   loopController.loop([&]() { loopController.stop(); });
-  auto v1 = f1.get();
-  auto v2 = f2.get();
+  auto v1 = std::move(f1).get();
+  auto v2 = std::move(f2).get();
 
   EXPECT_EQ(v1, testValue1);
   EXPECT_EQ(v2, testValue2);

folly/futures/test/Benchmark.cpp

@@ -319,7 +319,7 @@ BENCHMARK(lvalue_get) {
   Optional<Future<Bulky>> future;
   future = makeFuture(Bulky("Hello"));
   suspender.dismissing([&] {
-    std::string message = future.value().get().message();
+    std::string message = std::move(future.value()).get().message();
     doNotOptimizeAway(message);
   });
 }

folly/logging/test/AsyncFileWriterTest.cpp

@@ -256,7 +256,7 @@ TEST(AsyncFileWriter, flush) {
   readFull(readPipe.fd(), buf.data(), buf.size());
 
   // Make sure flush completes successfully now
-  future.get(10ms);
+  std::move(future).get(10ms);
 }
 
 // A large-ish message suffix, just to consume space and help fill up