Ticket #48896 - Default Setting for passwordMinTokenLength does not work
    
    Description: passwordMinTokenLength is supposed to be used for the
    length of comparison between the substring of obvious strings and
    a new password.  But it was not used to generate substrings.  This
    patch implements it.
    
    Also, old_pw was leaked in modify if password history was not enabled.
    
    https://fedorahosted.org/389/ticket/48896
    
    Reviewed by mreynolds@redhat.com (Thank you, Mark!)