L2SS-225: Replace bash -e in shebang with set -e

The bash -e shebang does not work on CentOS 7.

bootstrap/sbin/rebuild_system_from_scratch.sh

-#! /usr/bin/env bash -e
+#! /usr/bin/env bash
+
+set -e
 
 HOME_DIR=${LOFAR20_DIR:-${PWD}}
 if [ ! -d ${HOME_DIR}/bootstrap ]; then