Explicitly use bash

In the mailing list discussion, everyone seemed to agree that we
should just be explicit that these are bash scripts since that's
where we're testing them and there's no good way to ensure they
work on any other shells right now.

Change-Id: I86c41d2cddf6e91e7deeb4c2ab51635c80a1ce0c

elements/debian/root.d/08-debootstrap

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 #
 # Copyright 2014 Hewlett-Packard Development Company, L.P.
 # All Rights Reserved.

elements/opensuse/bin/install-packages

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright 2013 SUSE Linux Products GmbH
 # All Rights Reserved.

elements/opensuse/pre-install.d/01-install-bin

@@ -1,3 +1,3 @@
-#!/bin/sh
+#!/bin/bash
 
 install -m 0755 -o root -g root $(dirname $0)/../bin/* /usr/local/bin