dsdb: Allow password history and password changes without an NT hash

We now allow this to be via the ENCTYPE_AES256_CTS_HMAC_SHA1_96 hash instead
which allows us to decouple Samba from the unsalted NT hash for
organisations that are willing to take this step (for user accounts).

(History checking is limited to the last three passwords only, as
ntPwdHistory is limited to NT hash values, and the PrimaryKerberosCtr4
package only stores three sets of keys.)

Since we don't store a salt per-key, but only a single salt, the check
will fail for a previous password if the account was renamed prior to a
newer password being set.

Pair-Programmed-With: Stefan Metzmacher <metze@samba.org>

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
