[Python] Add configuration.{connection_pool_maxsize, assert_hostname} (#6508)

* Backport kubernetes client features:

- assert_hostname
- connection_pool_maxsize
- cleanups

* Update petstore sample

samples/client/petstore/python-asyncio/test/test_dog.py

@@ -0,0 +1,44 @@
+# coding: utf-8
+
+"""
+    Swagger Petstore
+
+    This spec is mainly for testing Petstore server and contains fake endpoints, models. Please do not use this for any other purpose. Special characters: \" \\
+
+    OpenAPI spec version: 1.0.0
+    Contact: apiteam@swagger.io
+    Generated by: https://github.com/swagger-api/swagger-codegen.git
+"""
+
+
+from __future__ import absolute_import
+
+import os
+import sys
+import unittest
+
+import petstore_api
+from petstore_api.rest import ApiException
+from petstore_api.models.dog import Dog
+
+
+class TestDog(unittest.TestCase):
+    """ Dog unit test stubs """
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def testDog(self):
+        """
+        Test Dog
+        """
+        # FIXME: construct object with mandatory attributes with example values
+        #model = petstore_api.models.dog.Dog()
+        pass
+
+
+if __name__ == '__main__':
+    unittest.main()