Tone alarm sim: Fix resource leak

src/platforms/posix/drivers/tonealrmsim/tone_alarm.cpp

@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (C) 2013 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2013, 2017 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -861,6 +861,7 @@ tone_alarm_main(int argc, char *argv[])
 			/* terminate the string */
 			buffer[sz] = 0;
 			ret = play_string(buffer, true);
+			fclose(fd);
 		}
 
 		/* if it looks like a PLAY string... */