steam_helper: Call FreeConsole before waiting to exit

Patch by Jacek Caban. This allows conhost to exit so it won't block server exit.

steam_helper/steam.cpp

@@ -695,6 +695,7 @@ int main(int argc, char *argv[])
 
     if(wait_handle != INVALID_HANDLE_VALUE)
     {
+        FreeConsole();
         WaitForSingleObject(wait_handle, INFINITE);
     }