ipalib.parameters: Handle 0-prefixed octal format of ints
    
    In Python 2, numbers prfixed with '0' are parsed as octal,
    e.g. '020' -> 16. In Python 3, the prefix is '0o'.
    
    Handle the old syntax for IPA's parameter conversion to keep
    backwards compatibility.
    
    Reviewed-By: Tomas Babej <tbabej@redhat.com>