In order to apply dynamically generated virt-type config to the actual
templates they need to be rendered.
Also improves a KVM presence check since the CPU features may be visible
to a container but KVM API via a character file might not be available
there.
The cpu-mode is now also set to "host-model" instead of "host-passthrough"
when emulation is used as it is done in the default config.
Closes-Bug: #1942761
Change-Id: I689543232a94f4df16445c6e3057c5a329d3f6ae
648a45f3d9