Pipeline custom (aws#2813)

* Pipelines Custom Callback Example * Pipelines Custom Callback Example * Pipelines Custom Callback Example * add IAM script * add IAM creation notice * catch EntityAlreadyExistsException errors * Fixed reference to EMR and ensure latest SDK Co-authored-by: Hamiti <hamitis@147ddadafbc7.ant.amazon.com> Co-authored-by: SofianHamiti <sofian.hamiti@gmail.com>

Author: 3 people