libct: createExecFifo: optimize

Every time we call container.Config(), a new copy of
struct Config is created and returned, and we do it twice here.

Accessing container.config directly fixes this.

Fixes: 805b8c73d ("Do not create exec fifo in factory.Create")
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

libcontainer/container_linux.go

@@ -432,11 +432,11 @@ func (c *Container) signal(s os.Signal) error {
 }
 
 func (c *Container) createExecFifo() (retErr error) {
-	rootuid, err := c.Config().HostRootUID()
+	rootuid, err := c.config.HostRootUID()
 	if err != nil {
 		return err
 	}
-	rootgid, err := c.Config().HostRootGID()
+	rootgid, err := c.config.HostRootGID()
 	if err != nil {
 		return err
 	}