CIFS: Make CAP_* checks protocol independent

Since both CIFS and SMB2 use ses->capabilities (server->capabilities)
field but flags are different we should make such checks protocol
independent.

Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>