This prevents the reuse of TOTP tokens by recording the last token
interval that was used. This will be replicated as normal. However,
this patch does not increase the number of writes to the database
in the standard authentication case. This is because it also
eliminates an unnecessary write during authentication. Hence, this
patch should be write-load neutral with the existing code.

Further performance enhancement is desired, but is outside the
scope of this patch.

https://fedorahosted.org/freeipa/ticket/4410

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

This change has two motivations:
  1. Clients don't have to parse the string.
  2. Future token types may have new formats.

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

Reviewed-By: Nathaniel McCallum <npmccallum@redhat.com>

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>

Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>