prototypes: xci: provision-vm-nodes: Do not provision VMs as root.

prototypes: xci: provision-vm-nodes: Do not provision VMs as root.

There is no need to provision VM nodes as root. The only thing that we
need to run as root is the destroy-env.sh script and for that we move
it to its own play so we can use Ansible's become directive. Moreover,
since this playbook operates on localhost we can use 'connection: local'
so we don't have to execute everything via ssh and possibly speed up
the whole process.

Change-Id: Ia9efd5f30e95385b5cf193dde352f93551846c0e
Signed-off-by: Markos Chandras <mchandras@suse.de>