fix cli scheduler:run breaks if --live-site does not end with /

[svanschu]

Pull Request for Issue https://github.com/joomla/joomla-cms/issues/42859

Summary of Changes

Adding a check if SCRIPT_NAME starts with a / or if $uri ends with a / If both checks are false add a / to prevent invalid URLs

Testing Instructions

testing described in https://github.com/joomla/joomla-cms/issues/42859

Documentation Changes Required