fsdev: fix memory leak in main()

@rpath and @sock_name are not freed and leaked.

[groug, not really leaked since the program exits just after that. But it
 is always good practice to free allocated memory]

Signed-off-by: Zhipeng Lu <lu.zhipeng@zte.com.cn>
Signed-off-by: Greg Kurz <groug@kaod.org>
