Description of problem:
When deploying RHVH, especially in self-hosted engine config, and a custom disk layout is selected, LVM Thin needs to be the default or at least an error needs to be thrown if it is not selected, otherwise the installation will fail.

Version-Release number of selected component (if applicable):
ISO image for RHVH - RHVH-4.0-20161018.0-RHVH-x86_64-dvd1.iso

How reproducible:
consistently every time

Steps to Reproduce:
1. deploy RHVH from ISO (DVD, USB, etc)
2. select custom disk layout, LVM (non-thin) is default
3. allow RHVH deployment to commence
4. deployment will fail as it requires LVM Thin

Actual results:
hosted engine fails because the disk layout requires LVM thin

Expected results:
RHVH custom disk layout should either default to LVM thin or throw an error stating that LVM thin is required