properly detach containers from network on 'weave reset'

since otherwise we are leaving veth pairs behind which a) breaks a
subsequent 'weave attach', and b) runs contrary to 'weave reset's
stated purpose of removing all traces of weave.

NB: This does yank the ethwe interface from the containers.

Fixes #164

weave

@@ -463,6 +463,9 @@ case "$COMMAND" in
         docker rm -f $CONTAINER_NAME >/dev/null 2>&1 || true
         check_command_and_run conntrack conntrack -D -p udp --dport $PORT >/dev/null 2>&1 || true
         destroy_bridge
+        for LOCAL_IFNAME in $(ip link show | grep v${CONTAINER_IFNAME}pl | cut -d ' ' -f 2 | tr -d ':') ; do
+            ip link del $LOCAL_IFNAME
+        done
         ;;
     *)
         echo "Unknown weave command '$COMMAND'" >&2