create_disk.sh: use /bin/bash interpreter
We're already using bashisms in this script, so this is just reflecting
reality.
As a plus, this makes the script no longer ignored by ShellCheck.
-#!/bin/sh
+#!/bin/bash
+set -euo pipefail
+
# This script is run in supermin to create a Fedora CoreOS style
# disk image, very much in the spirit of the original
# Container Linux (orig CoreOS) disk layout, although adapted
# although see also https://github.com/coreos/coreos-assembler/pull/298
# For people building "derived"/custom FCOS-like systems, feel free to file
# an issue and we can discuss configuration needs.
-set -euo pipefail
# This fixed UUID is detected in ignition-dracut and changed
# on firstboot:
