luci-mod-system: Add 'disabled' as cron log level

Add "Disabled" with value 9 as a choice for cron log level.

9 actually exceeds the highest built-in value 8, but can be
used to quieten the logging in cases where there are e.g. cron
jobs running each minute, which would create log spam.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

modules/luci-mod-system/htdocs/luci-static/resources/view/system/system.js

@@ -195,6 +195,7 @@ return view.extend({
 		o = s.taboption('logging', form.ListValue, 'cronloglevel', _('Cron Log Level'));
 		o.default = 7;
 		o.value(7, _('Normal'));
+		o.value(9, _('Disabled'));
 		o.value(5, _('Debug'));
 
 		/*