FreeBD diff reduction: generate and save the sshd host keys in gui instead of TrueOS.

Before this was being handled by modification to FreeBSD in TrueOS.

To remove the modification from FreeBSD we instead move the parts to extract the generated keys to ix-sshd which runs before /etc/rc.d/sshd and move the parts that save the keys to a new script ix_sshd_save_keys.

This allows us to remove the TrueOS patch  trueos/trueos@b82f03dbc266e9425bd38182b894caa4887e5f93

After this pull request is taken, then the commit to trueos should be reverted.