ceph: set correct cap mask for getattr request for read

In case of hitting the file EOF, ceph_read_iter() needs to retrieve the
file size from MDS, and Fr caps aren't neccessary.

[ idryomov: fold into existing retry_op == READ_INLINE branch ]

Reported-by: Frank Hsiao <frankhsiao@qnap.com>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Frank Hsiao <frankhsiao@qnap.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>