Fix a rare bug on shutdown.

src/cpp/ripple/InstanceCounter.h

@@ -50,6 +50,11 @@ public:
 		sMultiThreaded = true;
 	}
 
+	static void shutdown()
+	{
+		sMultiThreaded = false;
+	}
+
 	static bool isMultiThread()
 	{
 		return sMultiThreaded;

src/cpp/ripple/main.cpp

@@ -265,6 +265,7 @@ int main(int argc, char* argv[])
 		setupServer();
 		NameThread("io");
 		startServer();
+		InstanceType::shutdown();
 	}
 	else
 	{