systemd: set service type to notify.
Currently the service type is 'simple', the default, meaning that
docker.service is considered to be started straight after
spawning. This is incorrect as there is significant amount of time
between spawning and docker ready to accept connections on the passed
sockets. Docker does implement systemd socket activate and
notification protocol, and send the ready signal to systemd, once it
is ready. However for systemd to take those notifications into
account, the service file type should be set to notify.
Signed-off-by: Dimitri John Ledkov <dimitri.j.ledkov@intel.com>
(cherry picked from commit d3e5179c291a7646c71f1ca608d6700026756f7c)
Dimitri John Ledkov