This patch ensures that the authorized_keys ansible module, as well as
the built in "generate_ssh_keys" flag for user creation, so that we can
avoid using shell out commands.
Additionally, this moves the key synchronisation to use ansible
variables instead of the memcache server.
Change-Id: I0072b8d0977ab9aea10dd95080756f6864612013
Closes-Bug: #1477512