lib/aux: Plug memory leak in __igt_lsof_fds

Add a missing closedir call.
Signed-off-by: Petri Latvala <petri.latvala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

lib/igt_aux.c

@@ -1419,6 +1419,8 @@ again:
 		free(copy_fd_lnk);
 		free(fd_lnk);
 	}
+
+	closedir(dp);
 }
 
 /*