Skip the cert validator if the csr we are passed in is a valid filename
    
    The validator will still fire, just after the load_files() call. Basically
    it will hit the validator twice. The first time it will exit because the
    value of csr is a filename. The second time it will run the validator against
    the contents of the file.
    
    ticket https://fedorahosted.org/freeipa/ticket/1777