update python petstore samples

Author: wing328

samples/client/petstore/python-asyncio/petstore_api/api_client.py

@@ -63,7 +63,7 @@ class ApiClient(object):
     _pool = None
 
     def __init__(self, configuration=None, header_name=None, header_value=None,
-                 cookie=None, pool_threads=1):
+                 cookie=None, pool_threads=None):
         if configuration is None:
             configuration = Configuration()
         self.configuration = configuration

samples/client/petstore/python-tornado/petstore_api/api_client.py

@@ -64,7 +64,7 @@ class ApiClient(object):
     _pool = None
 
     def __init__(self, configuration=None, header_name=None, header_value=None,
-                 cookie=None, pool_threads=1):
+                 cookie=None, pool_threads=None):
         if configuration is None:
             configuration = Configuration()
         self.configuration = configuration

samples/client/petstore/python/petstore_api/api_client.py

@@ -63,7 +63,7 @@ class ApiClient(object):
     _pool = None
 
     def __init__(self, configuration=None, header_name=None, header_value=None,
-                 cookie=None, pool_threads=1):
+                 cookie=None, pool_threads=None):
         if configuration is None:
             configuration = Configuration()
         self.configuration = configuration