luci-app-zerotier: fix running

package/lean/luci-app-zerotier/luasrc/model/cbi/zerotier/settings.lua

@@ -23,4 +23,9 @@ e=t:option(DummyValue,"opennewwindow" ,
 	translate("<input type=\"button\" class=\"cbi-button cbi-button-apply\" value=\"Zerotier.com\" onclick=\"window.open('https://my.zerotier.com/network')\" />"))
 e.description = translate("Create or manage your zerotier network, and auth clients who could access")
 
+local apply = luci.http.formvalue("cbi.apply")
+if apply then
+	io.popen("/etc/init.d/zerotier restart")
+end
+
 return a