Revert "Update zerotier.stop (#3670)"

This reverts commit 8ed70658.

package/lean/luci-app-zerotier/root/etc/zerotier.stop

 #!/bin/sh
 
-zts=$(ifconfig | grep zt | awk '{print $1}')
-for zt0 in $zts
-do
+zt0=$(ifconfig | grep zt | awk '{print $1}')
 if [ "$zt0" = "" ]; then
   zt0=$(cat /tmp/cat /tmp/zt.nif)
 fi
@@ -12,4 +10,3 @@ iptables -D FORWARD -o $zt0 -j ACCEPT 2>/dev/null
 iptables -t nat -D POSTROUTING -o $zt0 -j MASQUERADE 2>/dev/null
 ip_segment=$(ip route | grep "dev $zt0 proto" | awk '{print $1}')
 iptables -t nat -D POSTROUTING -s $ip_segment -j MASQUERADE 2>/dev/null
-done