Fix storage_controller to show custom buttons
Fix storage_controller to show custom buttons

Closes https://github.com/ManageIQ/manageiq-ui-classic/issues/996

It cannot rely on @lastaction == 'show_list' because it's always 'explorer'. Introduced in https://github.com/ManageIQ/manageiq/pull/11793

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic