Add the cirros 0.3.0 test image

It takes 60 seconds to boot, 40 seconds less than 0.3.1.
But 0.3.1 has curl with https support.
Disable libvirt file injection

There is a problem with qemu-nbd where it never completes and hogs the cpu.
This feature is not needed as the keys etc can be got from the metadata
service.