daemon: translateContainerdStartErr(): use exit code 128 as default

After further looking at the code, it appears that the default exit-code
for unknown (other) errors is 128 (set in `defer`).

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/errors.go

@@ -176,6 +176,7 @@ func translateContainerdStartErr(setExitCode func(exitStatus), err error) error
 	}
 
 	// TODO: it would be nice to get some better errors from containerd so we can return better errors here
+	setExitCode(exitUnknown)
 	return errdefs.Unknown(errors.New(errDesc))
 }