Revert "iptables: build as static library"

This reverts commit be982317689d01b5f6252719069b86ad08107ddf.
iptables: fix install after revert to shared build

Signed-off-by: Stephan Raue <stephan@openelec.tv>
Merge branch 'master' of github.com:OpenELEC/OpenELEC.tv