Update change_targetref tests to fix azure DNS issue

[emmaaroche]

Description

Issue described in #696. This fix aims to help avoid inconsistent test failures when DNS records take time to propagate, especially on Azure.

What was the issue

Some change_targetref tests run before DNS is fully ready. Even though the DNSPolicy was created successfully, its status showed:

type: Enforced
status: 'False'
message: 'DNSPolicy has encountered some issues: policy is not enforced on any DNSRecord: not a single DNSRecord is ready'

With recordConditions stuck in:

reason: AwaitingValidation
status: 'False'
type: Ready

This caused test traffic to hit unresolved hostnames and fail with DNS-related errors (nodename nor servname provided).

Changes

• Refactored DNS readiness logic into the dns_policy2 fixture:

  • Waits for recordConditions to report "Ready" with status=True

  • Waits until the associated hostname successfully resolves (via is_nxdomain)

• This ensures tests don’t proceed until DNS is actually ready

Note: The helper is not used in the DNSPolicy test, that test is expected to hit a DNS failure.

Related issue

Closes #696.