Fix #94, generate and save the sshd host keys.

Before this was being handled by hacks to FreeBSD in TrueOS.

To remove the hack, 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.
Merge branch 'refactor_ssh_host_keys' of https://github.com/alfredperlstein/freenas into alfredperlstein-refactor_ssh_host_keys
Merge branch 'alfredperlstein-refactor_ssh_host_keys'