Switch to new region endpoints

Author: rayluo

msal/application.py

@@ -622,7 +622,7 @@ def _get_regional_authority(self, central_authority):
             else self._region_configured)  # It will retain the None i.e. opted out
         logger.debug('Region to be used: {}'.format(repr(region_to_use)))
         if region_to_use:
-            regional_host = ("{}.r.login.microsoftonline.com".format(region_to_use)
+            regional_host = ("{}.login.microsoft.com".format(region_to_use)
                 if central_authority.instance in (
                     # The list came from point 3 of the algorithm section in this internal doc
                     # https://identitydivision.visualstudio.com/DevEx/_git/AuthLibrariesApiReview?path=/PinAuthToRegion/AAD%20SDK%20Proposal%20to%20Pin%20Auth%20to%20region.md&anchor=algorithm&_a=preview

tests/test_e2e.py

@@ -904,7 +904,7 @@ def _test_acquire_token_for_client(self, configured_region, expected_region):
                 self.app.http_client, "post", return_value=MinimalResponse(
                 status_code=400, text='{"error": "mock"}')) as mocked_method:
             self.app.acquire_token_for_client(scopes)
-            expected_host = '{}.r.login.microsoftonline.com'.format(
+            expected_host = '{}.login.microsoft.com'.format(
                 expected_region) if expected_region else 'login.microsoftonline.com'
             mocked_method.assert_called_with(
                 'https://{}/{}/oauth2/v2.0/token'.format(