Postgres is used by several roles, but the setup is currently part of the 'mailserver' role. By moving it to 'common', it's possible to disable the mailserver without breaking the others.

The `private_key` variable used to check for changes was never
registered.

While adding the Let's Encrypt offline testing block in 1746afcc we
accidentially duplicated a the 'when' statement. Ansible only looks at
the last when statement for a given block meaning the earlier one has no
use. This commit merges both lines in one.

This is done to suppress warnings from ansible-lint.

The ``sudo`` and ``sudo_user`` directives are replaced with ``become``
and ``become_user`` in Ansible 1.9.

The installer automatically updates itself, which registers as a change
in the git repo.  To maintain idempotency of the task list, the repo
download must be forced.

Don't copy the LE certificates.  Instead use the ssl-cert group to
manage access to the LE certificates directly.  See
https://github.com/letsencrypt/letsencrypt/issues/1425 for a request to
have the LE client do this itself.

This method uses Subjective Alternative Names (SANs) to get one
certificate for all the subdomains that Sovereign employs, whether or
not the user configured their site with the roles.

Make a clean distinction between Debian 7 and Debian 8.  Anticipate the
next Ubuntu LTS release (Xenial) that is planned for support.