fix(profiles): use the right directory

this was still pointing at the chromiumos directory which meant that
/etc/ssh/sshd_config from net-misc/openssh wasn't getting filtered
causing coreos-base/coreos-base not to lay down our fixed config.
fix(coreos-base/coreos-base): re-enable sshd_config

re-enable installation of our custom ssh config that puts the keys on
/mnt/stateful_partition.