6in4: delete tunnel on interface teardown

Delete tunnel on 6in4 interface teardown.
Should solve problem related to tunnel stuck on restart loop
with "Unknown Command" on tunnel restart due to wan connection drop.
Fixes: FS#3690

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>

package/network/ipv6/6in4/Makefile

@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=6in4
-PKG_RELEASE:=26
+PKG_RELEASE:=27
 PKG_LICENSE:=GPL-2.0
 
 include $(INCLUDE_DIR)/package.mk

package/network/ipv6/6in4/files/6in4.sh

@@ -138,6 +138,8 @@ proto_6in4_setup() {
 
 proto_6in4_teardown() {
 	local cfg="$1"
+	local link="6in4-$cfg"
+	ip link del $link
 }
 
 proto_6in4_init_config() {