FEAT: add Image based installation of test VMs

[pcfe]

At the moment we only support kickstart installs for test VMs

FEAT: add support for image based installs.

Changes needed:

• hosts installed from Image do not offer the 'build' option
• delete the host instead of power-cycle (Destroy associated VM on host delete must be enabled in Satellite)
• create the host from image instead of power on after setting build=yes
• add pointer to Satellite Provisioning Guide to README

either adjust buildtestvms.sh or just write a separate script (to avoid drowning in if clauses) and adjust the Jenkinsfile

[pcfe]

will start by supporting

• libvirt

plan to add next

• OpenStack

not planned for now

• EC2
• vSphere
• RHEV

Patches, as always, welcome.

[pcfe]

note to self, quickest way to add the ssh pubkey of the jenkins user seems to be

virt-sysprep --add rhel-server-7.7-x86_64-kvm.qcow2 --ssh-inject root:file:/tmp/id_rsa.pub

Having a host with functional virt-sysprep will be a an acceptable prerequisite.