Switch scripts to use bash

This commit switches the command-line scripts to use bash instead of sh
so that we can take advantage of features that bash provides like
arrays.

Relates elastic/elasticsearch#2214

Original commit: elastic/x-pack-elasticsearch@826c10ef04

elasticsearch/license/licensor/bin/key-pair-generator

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/license/licensor/bin/license-generator

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/license/licensor/bin/verify-license

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/x-pack/bin/x-pack/extension

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/x-pack/shield/bin/x-pack/syskeygen

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/x-pack/shield/bin/x-pack/users

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;

elasticsearch/x-pack/watcher/bin/x-pack/croneval

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 # or more contributor license agreements. Licensed under the Elastic License;