test: Fix vm.install for non-LVM cloud images
test: Fix vm.install for non-LVM cloud images

Some of our images, like centos-8-stream, are already built from the official
cloud images instead of virt-install with LVM. More images are going to do that
soon [1], so fix vm.install to only do the LVM grow steps if the image actually
uses LVM.

[1] https://github.com/cockpit-project/bots/pull/1518

jkozol/welder-web,jkozol/welder-web,jkozol/welder-web,jkozol/welder-web