Automate OS Image template import for Nutanix

[abhay-krishna]

To test the OS images we build through image-builder for different providers, we need to import them into the corresponding compute management platforms, i.e. VMWare vCenter for OVAs, Nutanix Prism Central for Nutanix QCOW2 images, Apache CloudStack for CloudStack QCOW2 images, etc. Currently we only do this for the OVAs and CloudStack templates, through a nightly CodeBuild job. We must also extend this for the Nutanix hypervisor.