automation: qemu-smoke-arm64: Run ping test over a pv network interface

automation: qemu-smoke-arm64: Run ping test over a pv network interface

This patch modified the test in the following way
- Dom0 is booted with an alpine linux rootfs with the xen tools.
- Once Dom0 is booted, it starts xenstored, calls init-dom0less to setup
the xenstore interface for the dom0less Dom1, setups the bridged network
and attaches a pv network interface to Dom1.
- In the meantime, Dom1 in its init script tries to assign an ip to eth0
and ping Dom0,
- If Dom1 manages to ping Dom0, it prints 'passed'.

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>