SSHD Service extensions

SSHD Service extensions

This change adds an `include` statement to bring in the extra
functionality available from the existing puppet-ssh module in
already available in RDO.

By using puppet-ssh it provides a framework to allow the passing in of
server options using just hiera values under ssh::server_options.
For example, sshd_config banner can now be passed a server option, as
well as all the new parameters outlined in the launchpad issue that
the patch references for Closing. For this reason, the former augeas
setting for `Banner /etc/issue` is now managed by the main puppet-ssh
module instead.

The change also allows population of MOTD text to `/etc/motd` as
well as `issue.net`.

$bannertext is refactored in accordance with patch [1]

[1] https://review.openstack.org/#/c/442406/

Change-Id: Id329538fb7b623526f1d91d8a513cf3440c86a7c
Closes-Bug: 1668543