improve rfc4193 related integration test failures

[laduke]

re issue #209

they would fail sometimes so far so good with this change

this change inserts fd23:3cca:ac27:8e85:c199:9300::/88

instead of fd23:3cca:ac27:8e85:c199:93e7:50c5:1646/88 into the reverse ptr authority

actually it would insert 1 of each before

so there would be 2 SOA things, but only 1 would have the actual ptr records on it and then lookups would fail sometimes