Initial support for Nova in Ansible

Partially-Implements: blueprint ansible-service

Change-Id: I4b0a74bd3e5daa5664f5e1e622bfb40c3285949e

Partially Implements: Blueprint standard-start

Change-Id: I40a863161bee779a944e9388a1ad7d5d0e7adba7

Database syncs should not be required every time a container starts.
We can default database startup to true, but give the option
to set it to false.

Change-Id: Ib76876b2671f6c31f4511412efd3a438ec78f01f
Closes-bug: #1467576

The only files in the docker image directories that differ majorly between
distros are the Dockerfiles (e.g. different package manager mechanisms,
different repo sources, etc).

The supporting files such as the start.sh/check.sh and config files should
largely stay the same between base images.

This change moves these files up into a "common" directory, and symlinks them
in the same way that the build script is managed. This means when adding a new
base distro only new Dockerfiles need to be created. Also, if a distro does
happen to require a vastly different start.sh script for example, one can
choose to simply not symlink to the common and instead drop in a custom one.

Implements: blueprint refactor-base-image-layout

Change-Id: Ic4db69d31ff54a1fb95af4853a2e5ae490064284