Bug description
Mesh expansion does not work due to #13291

1. iptable-starts.sh stops on a mesh expansion VM instance.
2. Cluster.env file is

ISTIO_SERVICE_CIDR=10.43.240.0/20
ISTIO_SYSTEM_NAMESPACE=istio-system
ISTIO_CP_AUTH=MUTUAL_TLS

Expected behavior
istio-sidecar.deb package after installed on a VM, we are able to start Envoy side car.

Steps to reproduce the bug

1. Build sidecar Debian package, install it on a VM.
2. iptable-start.sh will fail at IsValidIP function

function isValidIP() {
   if [ "$1" != "${1#*[0-9].[0-9].[0-9].[0-9]}" ]; then
      true
   elif [ "$1" != "${1#*:[0-9a-fA-F]}" ]; then
      true
   else
      echo "not valid ip $1"
   fi
}
isValidIP "10.3.240.0"

output not valid ip 10.3.240.0, and the iptable setups stops.

More description can be found at #13291 (comment)