multiwan package: use less iptables -F

multiwan package: use less iptables -F

Hi

Even if "qos-scripts" package isn't installed, multiwan is flushing all the mangle chains.
This patch correct this behavior to let people use mangle table if qos-scripts is not there (to use there own qos script ...)

Info: For the moment the qos management of the multiwan package is broken (it's speaks about IMQ, instead of IFB)

The package version go from 1.0.20 to 1.0.21 (and not 1.0.19) because there is this patch also pending (http://patchwork.openwrt.org/patch/1740/)

Signed-off-by: Etienne CHAMPETIER <etienne.champetier@free.fr>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@30833 3c298f89-4303-0410-b956-a3cf2f4a3e73