Update WebexTeamsAPI object

We cannot use the `self.base_url` object property until after `self._session` is initialized, which needs an access token that for an OAuth flow needs access to the base URL.  To break this circular dependency, just use the base URL provided in the `base_url` parameter.

Author: cmlccie

webexteamssdk/api/__init__.py

@@ -131,8 +131,8 @@ def __init__(self, access_token=None, base_url=DEFAULT_BASE_URL,
 
         # Init AccessTokensAPI wrapper early to use for oauth requests
         self.access_tokens = AccessTokensAPI(
-            self.base_url, object_factory,
-            single_request_timeout=single_request_timeout
+            base_url, object_factory,
+            single_request_timeout=single_request_timeout,
         )
 
         # Check if the user has provided the required oauth parameters