Description of problem: When installing the 4.0 beta in the AZ eu-west-3 I am seeing the error below. Not sure whether it is specific to the AZ or my install config. 

~~~
# ./openshift-install create cluster
INFO Consuming "Install Config" from target directory 
INFO Creating cluster...                          
ERROR                                              
ERROR Error: Error applying plan:                  
ERROR                                              
ERROR 4 errors occurred:                           
ERROR 	* module.masters.aws_instance.master[1]: 1 error occurred: 
ERROR 	* aws_instance.master.1: Error launching source instance: Unsupported: The requested configuration is currently not supported. Please check the documentation for supported configurations. 
ERROR 	status code: 400, request id: c41bbcd7-f2dd-400c-bdd1-da85c6f183db 
ERROR                                              
ERROR                                              
ERROR 	* module.masters.aws_instance.master[0]: 1 error occurred: 
ERROR 	* aws_instance.master.0: Error launching source instance: Unsupported: The requested configuration is currently not supported. Please check the documentation for supported configurations. 
ERROR 	status code: 400, request id: f3a19b07-6d29-443c-9be7-09534ff83f0c 
ERROR                                              
ERROR                                              
ERROR 	* module.masters.aws_instance.master[2]: 1 error occurred: 
ERROR 	* aws_instance.master.2: Error launching source instance: Unsupported: The requested configuration is currently not supported. Please check the documentation for supported configurations. 
ERROR 	status code: 400, request id: 4a2c5725-e075-46dc-9ed0-8a50e02763c7 
ERROR                                              
ERROR                                              
ERROR 	* module.bootstrap.aws_instance.bootstrap: 1 error occurred: 
ERROR 	* aws_instance.bootstrap: Error launching source instance: Unsupported: The requested configuration is currently not supported. Please check the documentation for supported configurations. 
ERROR 	status code: 400, request id: 4ad6f74f-ae75-4ea8-9352-bdebe6b59f41 
ERROR                                              
ERROR                                              
ERROR                                              
ERROR                                              
ERROR                                              
ERROR Terraform does not automatically rollback in the face of errors. 
ERROR Instead, your Terraform state file has been partially updated with 
ERROR any resources that successfully completed. Please address the error 
ERROR above and apply again to incrementally change your infrastructure. 
ERROR                                              
ERROR                                              
FATAL failed to fetch Cluster: failed to generate asset "Cluster": failed to create cluster: failed to apply using Terraform 
~~~~

# vi install-config.yaml

apiVersion: v1beta1
baseDomain: rhcee.support
machines:
- name: master
  platform: {}
  replicas: 3
- name: worker
  platform: {}
  replicas: 3
metadata:
  creationTimestamp: null
  name: mahoney4test4
networking:
  clusterNetworks:
  - cidr: 10.128.0.0/14
    hostSubnetLength: 9
  machineCIDR: 10.0.0.0/16
  serviceCIDR: 172.30.0.0/16
  type: OpenshiftSDN
platform:
  aws:
    region: eu-west-3
pullSecret: '{"auths":{"cloud.openshift.com":{"auth":"blah","email":"emahoney"},"quay.io":{"auth":"blah","email":"emahoney"}}}'
sshKey: |
  ssh-rsa blah root@mahoneyrocks


Version-Release number of the following components:
# ./openshift-install version
./openshift-install v0.10.0


How reproducible:
Can repeat at will. 

Steps to Reproduce:
- ./openshift-install create install-config
- ./openshift-install create cluster


Actual results:
openshift-install fails with:

~~~
Error launching source instance: Unsupported: The requested configuration is currently not supported. Please check the documentation for supported configurations. 
ERROR 	status code: 400, request id: 4ad6f74f-ae75-4ea8-9352-bdebe6b59f41
~~~

Expected results:

Additional info:
Please attach logs from ansible-playbook with the -vvv flag