message: test: fix RuntimeFromNonWorkerThreads
  While working on I am getting
  consistent timeouts for this test.
  To repro the timeout, I added a sleep before step 2. After this change,
  I can't repro anymore.
  Risk: n/a (test only)
diff: @@ -623,25 +623,42 @@ TEST_F(StaticLoaderImplTest, RuntimeFromNonWorkerThreads) {
  // Now set up a test thread which verifies foo -> bar
  //
  // Then change foo and make sure the test thread picks up the change.
  + bool read_bar = false;
  + bool updated_eep = false;
  Thread::MutexBasicLockable mutex;
  Thread::CondVar foo_read;
  Thread::CondVar foo_changed;
  const Snapshot* original_thread_snapshot_pointer = nullptr;
  auto thread = Thread::threadFactoryForTest().createThread([&]() {
  + {
  Thread::LockGuard lock(mutex);
  EXPECT_EQ("bar", loader_->threadsafeSnapshot()->get("foo"));
  + read_bar = true;
  original_thread_snapshot_pointer = loader_->threadsafeSnapshot().get();
  EXPECT_EQ(original_thread_snapshot_pointer, loader_->threadsafeSnapshot().get());
  foo_read.notifyOne();
  + }
  + {
  + Thread::LockGuard lock(mutex);
  + if (!updated_eep) {
  foo_changed.wait(mutex);
  + }
  EXPECT_EQ("eep", loader_->threadsafeSnapshot()->get("foo"));
  + }
  });
  {
  Thread::LockGuard lock(mutex);
  + if (!read_bar) {
  foo_read.wait(mutex);
  + }
  loader_->mergeValues({{"foo", "eep"}});
  + updated_eep = true;
  + }
  +
  + {
  + Thread::LockGuard lock(mutex);
  foo_changed.notifyOne();
  EXPECT_EQ("eep", loader_->threadsafeSnapshot()->get("foo"));
  }
  