intermittent failures, needs to wait until every NS has the new TXT record

[dpocock]

Before proceeding, the hook will poll the NS to see if the TXT record has changed. It waits for the fastest NS to reply.

Not every NS will be ready at the same time. Sometimes one of the servers isn't ready for 2 or 3 minutes.

Therefore, it is necessary for the hook to poll every NS to check for the new/revised TXT record. If any one NS is not ready, the hook should not proceed.