shadowsocks-libev: ss-rules: nft rule cleanup on reload
Remove nft rules file generated by ss-rules if ss-rules was or should be
turned off for by configuration. Use "fw4 restart" instead of "fw4
reload" to force the runtime rule reloading
Ref: https://github.com/openwrt/packages/pull/17937#issuecomment-1207357037
Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>
(cherry picked from commit 04ee032699)