Pre-flight check for firewall

**What would you like to be added**:
We should have a pre-flight check on the admin machine to make sure boots ports are not blocked by a firewall
**Why is this needed**:
Because I spent over an hour troubleshooting boots when my firewall was enabled 😭😭😭

Search the Go code for admin-machine bootstrap or pre-flight checks and identify the boot ports that must be reachable. Define how a firewall check should run before bootstrapping and what actionable failure output should report; done means blocked required ports are detected before boots begin.

Written by the indexing model from the issue text.