Add ephemeral state preservation support to mysql

Element also needed some refactoring to work like other elements in the
collection.

Change-Id: Ie5d91f1f719cfb98dd8d10f0be2ff46b3be91e14
Make mysql.create-users section optional

Before this change, if it was not passed in the script that reads it
would error out because a single newline is not valid JSON.

Change-Id: I46b7cee31a391d5ff174992a8bf6f1af50236822
Remove mysql debian-sys-maint user

The way we build and install the package prevents this user from
being created and we don't need it anyway. Also this makes no sense
on Fedora/RHEL/SuSE.

Change-Id: Ib22388a660303065b93c3b284c1359b71faeeab8
Remove obsolete haveged and clean-apt from mysql

Element is carrying old install scripts that are not necessary.

Change-Id: Ie10bdb407781a8e2bf973b0635634326173b8701
Remove any accidental extra /etc/my.cnf

Some platforms have packages that install /etc/my.cnf which would not
work well with our element which wants the configs in /etc/mysql.

Change-Id: Ifda1cca7287fae37eb8587598f5fab60228d8e99