cloud-init to manage /etc/hosts
1) Ubuntu includes a line in /etc/hosts that makes the local hostname and
nodename (if different) point to 127.0.1.1. This can break RabbitMQ,
which expects the hostname to resolve to the API network address.
2) The distribution might come with cloud-init installed, and manage_etc_hosts
configuration enabled. If so, it will override the file /etc/hosts from cloud-init
templates at every boot, which will break RabbitMQ.
This change fixes these issues.
Change-Id: I53261d0403b983ab419bd44e705b89f7b7a1c316
Closes-Bug: #1837699
0b24a0f2f0