switch button not updating when 'default' is 'on'

[bfiessinger]

Currently with a configuration like

$cmb2_box->add_field( [
	'name'			=> 'some name',
	'desc'			=> 'some desc',
	'id'				=> 'some_id',
	'type'			=> 'switch_button',
	'default'		=> 'on'
] );

the switch_button won't update the checked status after saving settings.