FIX: WorkflowApplicable::updateCMSActions()
FIX: WorkflowApplicable::updateCMSActions()

Prevent `ActionMenus.WorkflowOptions` from being added multiple times, if updateCMSActions() is called from other extensions
fixes #294
silverstripe-terraformers/advancedworkflow,silverstripe-australia/advancedworkflow,silverstripe-australia/silverstripe-advancedworkflow,silverstripe-terraformers/advancedworkflow,silverstripe-australia/advancedworkflow,silverstripe-australia/silverstripe-advancedworkflow