ceph: size handling in MClientRequest, cap updates and inode traces

For encrypted inodes, transmit a rounded-up size to the MDS as the
normal file size and send the real inode size in fscrypt_file field.
Also, fix up creates and truncates to also transmit fscrypt_file.

When we get an inode trace from the MDS, grab the fscrypt_file field if
the inode is encrypted, and use it to populate the i_size field instead
of the regular inode size field.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Reviewed-and-tested-by: Luís Henriques <lhenriques@suse.de>
Reviewed-by: Milind Changire <mchangir@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>