pkg: listeners: separate out the listeners package

This code will be used in containerd and is quite useful in general to
people who want a nice way of creating listeners from proto://address
arguments (even supporting socket activation). Separate it out from
docker/ so people can use it much more easily.

Signed-off-by: Aleksa Sarai <asarai@suse.de>

docker/daemon.go

@@ -26,11 +26,11 @@ import (
 	"github.com/docker/docker/cliconfig"
 	"github.com/docker/docker/daemon"
 	"github.com/docker/docker/daemon/logger"
-	"github.com/docker/docker/docker/listeners"
 	"github.com/docker/docker/dockerversion"
 	"github.com/docker/docker/libcontainerd"
 	"github.com/docker/docker/opts"
 	"github.com/docker/docker/pkg/jsonlog"
+	"github.com/docker/docker/pkg/listeners"
 	flag "github.com/docker/docker/pkg/mflag"
 	"github.com/docker/docker/pkg/pidfile"
 	"github.com/docker/docker/pkg/signal"