Add back exit when writer thread has finished

src/h5_zmq_writer.cpp

@@ -81,6 +81,9 @@ void write_h5(WriterManager *manager, RingBuffer *ring_buffer, string output_fil
     #ifdef DEBUG_OUTPUT
         cout << "[h5_zmq_writer::write] Writer thread stopped." << endl;
     #endif
+
+    // Exit when writer thread has finished.
+    exit(0);
 }
 
 void receive_zmq(WriterManager *manager, RingBuffer *ring_buffer, string connect_address, int n_io_threads=1, int receive_timeout=-1)