For some reason the support for init.d and thereby userinit.d has been removed from CyanogenMod starting with CM12. Unfortunately it is not easy to re-activate the functionality, even more so if you want the change to survive future CM updates.
So I decided to create a trivial app that will simply execute run-parts on the /data/local/userinit.d directory when the phone completes booting to get the good old userinit.d back. To clone the git repository run:
git clone https://lisas.de/~alex/runuserinit.git
Find more details on the repository contents here.
After installation you will have to start RunUserinit once and hit the button. When asked whether RunUserinit should be allowed to use root privileges accept that and make the setting permanent. Finally sshd will run automatically again, whenever my phone requires a reboot…