Commit a7fdc6c introduced a regression where file descriptors are opened
using O_PATH option. mac_smack_apply_fd() calls fsetxattr() and would fail
with a -EBADF (Bad file descriptor) error.
Use FORMAT_PROC_FD_PATH(fd) to convert the fd back into a full path and
call setxattr() or setfilecon() instead.
Signed-off-by: Donald Chan <hoiho@amazon.com>
