server: free strduped port numbers

Although the leak is negligible, the clean heap on exit will ease
valgrind testing.

Change-Id: I3a7a9c8e8dc7557aa51d0b9caa244537e5e7007d
Signed-off-by: Tomas Vanek <vanekt@fbl.cz>
Reviewed-on: http://openocd.zylin.com/4410
Tested-by: jenkins

src/openocd.c

@@ -345,6 +345,9 @@ int openocd_main(int argc, char *argv[])
 	/* Start the executable meat that can evolve into thread in future. */
 	ret = openocd_thread(argc, argv, cmd_ctx);
 
+	gdb_service_free();
+	server_free();
+
 	unregister_all_commands(cmd_ctx, NULL);
 
 	/* Shutdown commandline interface */