CONFIGURE: Fix detection of pylint
    
    If configure script was executed with --enable-pylint then
    it behaved the same as --disable-pylint. It does not make
    any sense.
    
    Resolves:
    https://fedorahosted.org/freeipa/ticket/6604
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Tomas Krizek <tkrizek@redhat.com>