Fixing configure-vm script and vm.xml with this patch because for
latest OS like centos8 - older python version and older qemu machine
type is causing issue.
* For configure-vm.py - Replacing python with python3 in environment
path as python3 is the default in many latest OS.
* For vm.xml - Replacing Machine type from pc-1.0 to pc.
- pc-1.0 is old and unsupported machine type for Centos8
- Moving machine type from pc-1.0 to pc will help as pc have alias to
supported qemu machine type
Related-Bug: #1875681
Change-Id: Icd7e98ceb8859f730a32981a150f2730bde9836b