py3: pass raw entries to LDIFWriter
    
    LDIFWriter.unparse() expects the scalar values of the attributes
    of the entries to be bytes as it applies a byte regular expression
    to check whether to base64-encode the values or not. Previously,
    we were passing the scalar attribute values as strings which
    was breaking the LDIFWriter.unparse() exectution.
    
    https://pagure.io/freeipa/issue/7131
    
    Reviewed-By: Felipe Barreto <fbarreto@redhat.com>