The docker-ce package depends on docker-ce-cli unconstrained, this
can lead to problems where the cli package is too new to communicate
with the daemon. This patch adds an explicit install task for the
cli package, so that it's version can be overridden if necessary.

Related conjurinc/ops#569

Permit to provide proxies for installation

* Do not use loop on package module with squash_actions

* Replace with_items with loop

* Revert "Replace with_items with loop"

This reverts commit e30627ff8be83f8fe59f009b5f0240cc2939e7d8.

* Bump Ansible version to 2.3

added flag to control UFW forward policy

When using the linux-aws kernel package for EC2 instances, there are no
linux-image-extra packages. However, the kernel image package itself already
contains AuFS support, so the installation can just be skipped.

Prepare for Ansbile 2.5 deprecations

Resolving following:
ERROR [role] ./defaults/main.yml:105:1: [error] too many blank lines (1 > 0) (empty-lines)

Treating no_proxy as http_proxy and https_proxy

* Allow selection of apt channel

This allows easier installation of nightly or edge releases.

* Clarify why you might want a different apt channel

* Revert "add var start_docker_daemon to only (re)start docker daemon if it is true (#204)"

This reverts commit f9abb68106e8b7076cf7549826091b2542e5f5d8.

* Revert "Flush fixes and adjustment to default bridge ip option"

This reverts commit b5a0deb1bfcf7ffe58c271c08cdf391724bbc96e.