Fix Pylint upgrade issues

* Remove unsupported pylint disable options
    * star-args removed in Pylint 1.4.3
    * abstract-class-little-used removed in Pylint 1.4.3

* Fixes new lint errors

* Copy dummy-variable-rgx expression to new ignored-argument-names expression to ignore unused funtion arguments

* Notable changes
    * Refactor to satisfy Pylint no-else-return warning
    * Fix Pylint inconsistent-return-statements warning
    * Refactor to satisfy consider-iterating-dictionary
    * Remove methods with only super call to satisfy useless-super-delegation
    * Refactor too-many-nested-statements where possible
    * Suppress type checked errors where member is dynamically added (notably derived from josepy.JSONObjectWithFields)
    * Remove None default of func parameter for ExitHandler and ErrorHandler

Resolves #5973

certbot-dns-rfc2136/certbot_dns_rfc2136/dns_rfc2136.py

@@ -220,4 +220,3 @@ class _RFC2136Client(object):
         except Exception as e:
             raise errors.PluginError('Encountered error when making query: {0}'
                                      .format(e))
-

certbot-dns-rfc2136/certbot_dns_rfc2136/dns_rfc2136_test.py

@@ -171,7 +171,7 @@ class RFC2136ClientTest(unittest.TestCase):
         result = self.rfc2136_client._query_soa(DOMAIN)
 
         query_mock.assert_called_with(mock.ANY, SERVER, port=PORT)
-        self.assertTrue(result == True)
+        self.assertTrue(result)
 
     @mock.patch("dns.query.udp")
     def test_query_soa_not_found(self, query_mock):
@@ -181,7 +181,7 @@ class RFC2136ClientTest(unittest.TestCase):
         result = self.rfc2136_client._query_soa(DOMAIN)
 
         query_mock.assert_called_with(mock.ANY, SERVER, port=PORT)
-        self.assertTrue(result == False)
+        self.assertFalse(result)
 
     @mock.patch("dns.query.udp")
     def test_query_soa_wraps_errors(self, query_mock):