nxemu-os: add NetworkInstance instance in core and clean up interrupt_pipe_fd on Finalize (#412)

src/nxemu-os/core/core.cpp

@@ -308,6 +308,9 @@ struct System::Impl {
     /// Services
     std::unique_ptr<Service::Services> services;
 
+    /// Network instance
+    Network::NetworkInstance network_instance;
+
     std::unique_ptr<Core::PerfStats> perf_stats;
     Core::SpeedLimiter speed_limiter;
 

src/nxemu-os/core/internal_network/network.cpp

@@ -188,9 +188,11 @@ void Initialize() {
 void Finalize() {
     if (interrupt_pipe_fd[0] >= 0) {
         close(interrupt_pipe_fd[0]);
+        interrupt_pipe_fd[0] = -1;
     }
     if (interrupt_pipe_fd[1] >= 0) {
         close(interrupt_pipe_fd[1]);
+        interrupt_pipe_fd[1] = -1;
     }
 }