add ipv{4,6}_dhcp_iaid* tests
Add test covering IAID property, so far tested values are unset ('ifname'), 'ifname' and 'mac'. Value 'perm-mac' not working on veths, but behaves similarly to 'mac'
Add test covering IAID property, so far tested values are unset ('ifname'), 'ifname' and 'mac'. Value 'perm-mac' not working on veths, but behaves similarly to 'mac'