ceph: fix inode leak on getattr error in __fh_to_dentry

Fixes: 878dabb6 ("ceph: don't return -ESTALE if there's still an open file")
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>