Name the ingress sandbox explicitly

Signed-off-by: Santhosh Manohar <santhosh@docker.com>

libnetwork/controller.go

@@ -920,6 +920,7 @@ func (c *controller) NewSandbox(containerID string, options ...SandboxOption) (s
 
 	if sb.ingress {
 		c.ingressSandbox = sb
+		sb.id = "ingress_sbox"
 	}
 	c.Unlock()
 	defer func() {