Ticket 50900 - Fix cargo offline build
    
    Bug Description: The cargo offline build was broken due to a missing
    + on the CPP flags to nsslapd, and because of a "space" between a
    variable and the value in configure.ac.
    
    Fix Description: Add the plus, remove the space.
    
    https://pagure.io/389-ds-base/pull-request/50900
    
    Author: William Brown <william@blackhats.net.au>
    
    Review by: mhonek (Thanks!)