tap-bridge: Update shell choice for scripts

src/tap-bridge/examples/virtual-network-setup.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 brctl addbr br-left
 brctl addbr br-right
 tunctl -t tap-left

src/tap-bridge/examples/virtual-network-teardown.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 lxc-stop -n left
 lxc-stop -n right
 lxc-destroy -n left