luci-app-keepalived: fix nopreempt value handling

The 'nopreempt' option is marked with the prefix 'no_value_' in the
keepalived init script. This means that if the value is not set in the
keepalived configuration, it must be removed from the uci configuration.

To get this behavior, the rmempty flag in the LuCI must be removed.

fixes #7114

Signed-off-by: Florian Eckert <fe@dev.tdt.de>

applications/luci-app-keepalived/htdocs/luci-static/resources/view/keepalived/vrrp_instance.js

@@ -64,8 +64,8 @@ return view.extend({
 			_('Allows the lower priority machine to maintain the master role,') +
 			_('even when a higher priority machine comes back online.') + ' ' +
 			_('For this to work, the initial state of this entry must be BACKUP.'));
+		o.optional = true;
 		o.default = false;
-		o.rmempty = false;
 
 		ipaddress = uci.sections('keepalived', 'ipaddress');
 		o = s.taboption('general', form.DynamicList, 'virtual_ipaddress', _('Virtual IP Address'),