Use more portable shebangs for bash scripts

terraform/openstack/scripts/install.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -e
 
 # Read the address to join from the file we provisioned

terraform/openstack/scripts/server.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -e
 
 # Read from the file we created

terraform/openstack/scripts/service.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -e
 
 echo "Starting Consul..."