Description of problem:
With version 2.3 and future 2.4 the AWS instances get deployed with a boot device hosted on IO1 storage class. We whould let customers decide, for cost reasons' which storage class is to be used gp2 or io1

Version-Release number of selected component (if applicable):
2.3 and later

How reproducible:
Every time

Steps to Reproduce:
1. Deploy a cluster via the RHACM console
2. Check the install-config.yaml generated. io1 is specified in config file
3. Check the volumes used by each instance. All reported as io1 based

Actual results:
controlPlane:
  hyperthreading: Enabled
  name: master
  replicas: 3
  platform:
    aws:
      zones:
      - us-east-2a
      - us-east-2b
      - us-east-2c
      rootVolume:
        iops: 4000
        size: 200
        type: io1
      type: m5.4xlarge

Expected results:
Varies depending on storage class chosen or none if gp2 selected

Additional info:
Full install-config generated
apiVersion: v1
metadata:
  name: 'ocp45dr'
baseDomain: ocstraining.com
controlPlane:
  hyperthreading: Enabled
  name: master
  replicas: 3
  platform:
    aws:
      zones:
      - us-east-2a
      - us-east-2b
      - us-east-2c
      rootVolume:
        iops: 4000
        size: 200
        type: io1
      type: m5.4xlarge
compute:
- hyperthreading: Enabled
  name: 'worker'
  replicas: 0
  platform:
    aws:
      rootVolume:
        iops: 2000
        size: 200
        type: io1
      type: i3en.3xlarge
      zones:
      - us-east-2a
      - us-east-2b
      - us-east-2c
networking:
  networkType: OpenShiftSDN
  clusterNetwork:
  - cidr: 10.116.0.0/14
    hostPrefix: 23
  machineNetwork:
  - cidr: 10.1.0.0/16
  serviceNetwork:
  - 172.31.0.0/16
platform:
  aws:
    region: us-east-2
pullSecret: "" # skip, hive will inject based on it's secrets
sshKey: |-
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