tc: don't set protococol field on filter delete

tc: don't set protococol field on filter delete

> # tc filter show dev eth1 | grep 4:29:d1
> filter parent 1: protocol ip pref 5 u32 fh 4:29:d1 order 209 key ht 4
> bkt 29 flowid 1:b7aa
>
> # tc filter del dev eth1 parent 1: pref 5 handle 4:29:d1 u32
> RTNETLINK answers: Invalid argument
> We have an error talking to the kernel
>
> after rollback to package"sys-apps/iproute2-2.6.24.20080108" all
> deleted normal...

The current iproute version uses "protocol all" by default
if its not specified. This is actually only useful for creating
new filters, on deletion an unset protocol is treated as wildcard.