crypto: drop secauth and make crypto none work again

keep totem.secauth config key for compatibility

if the key is NOT set, crypto will default to aes256/sha1
if the key is set to "off", crypto is disabled.
this reflects pretty much old behavior

keywords totem.crypto_cipher and totem.crypto_hash can
override secauth individually.

Signed-off-by: Fabio M. Di Nitto <fdinitto@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>