Log warning instead of ignoring unsupported cdn host configuration

The current use case is that we need to specify https:// explicitly since the url is also used in generated json files which are used by a third party app. The current implementation logs and error and ignores the setting if the url does not start with '//' or ends with '/'. The attached patch changes this behavior so that a warning is logged but the value is used hence giving back the control (to break) back to developers.

There are no functional changes except for relaxing the strictness on the configuration value.