libcgroup: fixed chmod cg_chmod_recursive_controller
libcgroup: fixed chmod cg_chmod_recursive_controller

fts_read can return NULL in two cases. Either when we have visited all
files in the hierarchy (when errno is set to 0) or when an error
occured. We shouldn't set an error code in the first case obviously.

Changelog since v1:
 - updated log message

Signed-off-by: Jan Safranek <a7f4b96ffdd515ecef00f117294da18555749b0b@redhat.com>
Reviewed-by: Michal Hocko <829500b200af6c2a0eca4dfd5c388e6b8fbe8dc6@suse.cz>

jrfastab/Linux-cgdcbxd,jrfastab/Linux-cgdcbxd,rafalmiel/libcg,jrfastab/Linux-cgdcbxd,rafalmiel/libcg,rafalmiel/libcg,rafalmiel/libcg,jrfastab/Linux-cgdcbxd