nut: Update server config comment 'docs'

Update the commented out settings in /etc/config/nut_server that
shows the available sections with their default settings.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

net/nut/files/nut_server

@@ -1,8 +1,9 @@
+#config driver_global 'driver_global'
+#	option user nut
+
 #config driver 'upsname'
 #	option driver usbhid-ups
 #	option port auto
-#	option other other-value
-#	option runas root
 
 #config user
 #	option username upsuser