netifd: fix jail ifdown and jails without jail_ifname

The previous commit introduced a regression for netns jails without
jail_ifname set. Fix that.

Fixes: 4e4f7c6d2d ("netifd: network namespace jail improvements")
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

package/network/config/netifd/Makefile

@@ -1,13 +1,13 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=netifd
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL=$(PROJECT_GIT)/project/netifd.git
 PKG_SOURCE_DATE:=2020-04-14
-PKG_SOURCE_VERSION:=d93126d3b91ea9e3831b9fd0b5318989f82daebe
-PKG_MIRROR_HASH:=d0b3fdc5a3fc55dff50ddd361ad1a90e4675e9697b8ba916bfe52ee4f24a6ca3
+PKG_SOURCE_VERSION:=dbf97b47a53809a6ff812d4466d2082aa4d3efb6
+PKG_MIRROR_HASH:=c46c4c12edcf5a869b8d84197700415e538d3e4d5f1cbe35e2baa30f15d49a17
 PKG_MAINTAINER:=Felix Fietkau <nbd@nbd.name>
 
 PKG_LICENSE:=GPL-2.0