Bug: AWS Cluster Controller attempts to install in /30 subnets

[faangbait]

Relevant log output:

awscluster_controller.go:327 msg="failed to create subnet: InvalidSubnet.Range: The CIDR '10.1.7.192/30' is invalid."

Possibly relevant: https://issues.redhat.com/browse/OCPBUGS-35054

Steps to replicate

This error occurred while attempting to replicate our 4.15.27 installation using 4.16.35.

On 4.15.27, the installer was creating /28 subnets. On 4.16.35, it's creating /30s. /30s are illegal on AWS, per AWS docs

Our Machine CIDR is defined as a /24 that exactly matches our VPC CIDR.

[faangbait]

Confirmed same error on 4.17.17.

It creates a /27, then attempts to create several /30s. The /27 is fine, the /30s fail.

[faangbait]

Is it just me, or did the number of subnets being created jump from ~8 to ~12 (AWS/6 AZs) between 4.15 and 4.16?

This might explain why the installer thought it needed to split its cidr into /30s -- but it shouldn't. You can fit 16 /28 subnets on a /24