AD: Never store case_sensitive as "true" to confdb
    
    If case_sensitive was set 'true' for AD
    backend, we ignore it and continue with AD
    default (false). However we still set confdb
    to whatever was set in sssd.conf for the
    responders. We should store to confdb
    the value that is used by the backend.
    
    Also fixes some misleading DEBUG messages
    in that code area.
    
    Reviewed-by: Pavel Reichl <preichl@redhat.com>