Currently, the `master.ign` contains the URL from which to download the actual Ignition. On cloud platforms, this value is:
"source":"https://api-int.<cluster domain>:22623/config/master"

Update this value with the API-Int LB IP when custom-dns is enabled on the GCP platform. 

User Story:

As a (user persona), I want to be able to:

• Capability 1
• Capability 2
• Capability 3

so that I can achieve

• Outcome 1
• Outcome 2
• Outcome 3

Acceptance Criteria:

Description of criteria:

• Upstream documentation
• Point 1
• Point 2
• Point 3

(optional) Out of Scope:

Detail about what is specifically not being delivered in the story

Engineering Details:

• (optional) https://github/com/link.to.enhancement/
• (optional) https://issues.redhat.com/link.to.spike
• Engineering detail 1
• Engineering detail 2

This requires/does not require a design proposal.
This requires/does not require a feature gate.