IPaddr2: CLUSTERIP start fails with nftables

It seems that with a recent kernel (4.19.13) and iptables (1.8.2) CLUSTERIP module does not start anymore:
```
Jan 16 10:28:27 sid1 IPaddr2(cip:1)[18653]: ERROR: iptables failed
Jan 16 10:28:27 sid1 pacemaker-execd[711]: notice: cip:1_start_0:18653:stderr [ iptables v1.8.2 (nf_tables): RULE_INSERT failed (Operation not supported): rule in chain INPUT ]
Jan 16 10:28:27 sid1 pacemaker-execd[711]: notice: cip:1_start_0:18653:stderr [ ocf-exit-reason:iptables failed ]
```
Kernel log reports:
```
[70159.456298] ipt_CLUSTERIP: ClusterIP Version 0.8 loaded successfully
[70159.458756] ipt_CLUSTERIP: cannot use CLUSTERIP target from nftables compat
```
Perhaps using an equivalent nftables command would work here.

Start at the IPaddr2 CLUSTERIP start path and reproduce the reported failure with kernel 4.19.13 and iptables 1.8.2 using the supplied logs. Investigate the nftables compatibility limitation and verify that CLUSTERIP starts successfully through a supported command path, with regression coverage if the existing test structure exposes this agent.

Written by the indexing model from the issue text.