Avoid new cert / ELB error
Avoid new cert / ELB error

There is a race condition in Terraform when it creates an ELB with a newly created certificate:

```
* aws_elb.concourse: Failure adding new or updated ELB listeners: DuplicateListener: A listener already exists for colin-cert-concourse with LoadBalancerPort 443, but with a different InstancePort, Protocol, or SSLCertificateId
status code: 400, request id: 3a2ed326-c5ce-11e5-9f46-a5c7d320375f
```
Here we add a sleep to give time to the IAM certificate to propagate.
An issue was raised: https://github.com/hashicorp/terraform/issues/4880

alphagov/paas-cf,jimconner/paas-cf,jimconner/paas-cf,jimconner/paas-cf,jimconner/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf,jimconner/paas-cf,jimconner/paas-cf,jimconner/paas-cf,alphagov/paas-cf,alphagov/paas-cf,alphagov/paas-cf