Reported by Christopher Baines <mail@cbaines.net>
at <https://lists.gnu.org/archive/html/guix-devel/2017-12/msg00058.html>.
* gnu/services/ssh.scm (<openssh-configuration>)[%auto-start?]: New
field.
(openssh-shepherd-service): Honor it.
* gnu/system/install.scm (%installation-services): Set '%auto-start?' to
#f for openssh-service-type.