sd-notify: do not hang when NOTIFY_SOCKET is used with create

if NOTIFY_SOCKET is used, do not block the main runc process waiting
for events on the notify socket.  Bind mount the parent directory of
the notify socket, so that "start" can create the socket and it is
still accessible from the container.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

start.go

@@ -3,6 +3,7 @@ package main
 import (
 	"errors"
 	"fmt"
+	"os"
 
 	"github.com/opencontainers/runc/libcontainer"
 	"github.com/urfave/cli"
@@ -31,7 +32,17 @@ your host.`,
 		}
 		switch status {
 		case libcontainer.Created:
-			return container.Exec()
+			notifySocket, err := notifySocketStart(context, os.Getenv("NOTIFY_SOCKET"), container.ID())
+			if err != nil {
+				return err
+			}
+			if err := container.Exec(); err != nil {
+				return err
+			}
+			if notifySocket != nil {
+				return notifySocket.waitForContainer(container)
+			}
+			return nil
 		case libcontainer.Stopped:
 			return errors.New("cannot start a container that has stopped")
 		case libcontainer.Running: