Cloud-Init add support for monitoring-agent

This patch adds support for monitoring-agent configuration section in
cloud-init

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Monitor-Agent support for cloud-init

This patch add supports for enabling/disblaing monitor-agent via
cloud-init. By default monitor-agent is enabled. Monitor agent
configuration structure
monitor-agent:
  enable: true/false

This patch also updates the message provided to users

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>