iptables: Correctly remove Cilium chains when IPv6 is disabled
iptables: Correctly remove Cilium chains when IPv6 is disabled

The Cilium chain removal in RemoveRules() was made dependent on IPv6 being
enabled, this is incorrect and leads to the following error when Ipv6 is
disabled:

```
level=warning msg="iptables: Chain already exists." subsys=iptables
level=error msg="Error while initializing daemon" error="cannot add custom chain CILIUM_OUTPUT: exit status 1" subsys=daemon
```

Fixes: 5b17c993e57 ("datapath/iptables: Check iptables kernel modules")

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

tklauser/cilium,cilium/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,cilium-team/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium-team/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium