Step buttons are enabled if you reload the page or access the Distribution Wizard while the installation is in progress

The step buttons (Continue, Later, Never) are normally disabled while the step performs its action (e.g. while the main wiki UI is installing). But if you reload the page or access the Distribution Wizard by chance while it is in progress the step buttons are enabled and so you can click them by mistake.

The issue is that the step buttons are disabled by the JavaScript code only when the step action is started. We need to disable them when the step is loaded if the step job is already running or waiting for user input.