containerd is now running as a separate service, and should
no longer be started as a managed child-process of dockerd.
The dockerd service already specifies that it should be started
`After` the containerd.service, but there is still a race
condition, where containerd is started, but its socket is not yet
created.
In that situation, `dockerd` detects that the containerd socket
is missing, and will start a new instance of containerd (as a
managed child-process), which causes live-restore to fail.
This patch explicitly sets the `--containerd` daemon option.
If this option is set, `dockerd` will not start a new instance
of containerd.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
23c763ef1c