clarify comments in site_sshd::authorized_keys

Change-Id: I679dfe8dff90b7c86ab0ffff43e13958f1ec2c99
Switch away from site_config::sshd and instead just include site_sshd

The existing site_config::sshd had a non-functioning 'include sshd' line
in it that was not doing what was expected (this was supposed to include
the sshd module, but due to scoping was including itself).

It seemed better to eliminate some of the unused pieces and consolidate
into one config location.

Change-Id: I79dd904e696ca646180a09abbb03b5361dfc8ab9
Update sshd submodule to get necessary fixes to enable us to change sshd port

Change-Id: I3b6a87c9d6a2c349392e5bc98a68b800645fde92
Add missing scope to top-level sshd class, passing necessary parameters
for configuration (#3108)

Change-Id: I4f94a47d47a40bfc6835359e7781707f96e91db0