Add an Amazon template for building AMIs

Add an Amazon template for building AMIs

The differences between this builder and the openstack one are the cloud
specific options passed, and the disabling of ANSIBLE_PIPELINING.

For some reason ansible is not able to set up the local ssh connection
(ssh <ssh_user>@127.0.0.1) on the EC2 instance after transfering the
playbook files, yet it can successfully ssh to the machine.

Disabling the pipelining support opens a new ssh connection each time
ansible runs a task. This takes more time, but works.

This patch also includes an amazon cloud example var file.

Change-Id: I2b9f273e86fd7bc1ddfde34d26eebfd6249a6a0a
Signed-off-by: Trevor Bramwell <tbramwell@linuxfoundation.org>