Require current password when using passwd to change your own password.
Add a new required parameter, current_password. In order to ask this
first I added a new parameter option, sortorder. The lower the value the
earlier it will be prompted for.
I also changed the way autofill works. It will attempt to get the default
and if it doesn't get anything will continue prompting interactively.
Since current_password is required I'm passing a magic value that
means changing someone else's password. We need to pass something
since current_password is required.
The python-ldap passwd command doesn't seem to use the old password at
all so I do a simple bind to validate it.
https://fedorahosted.org/freeipa/ticket/1808