Merge branch 'osw-use-bash-for-background-jobs-script' into 'master'

Use bash for bin/background_scripts

See merge request gitlab-org/gitlab!27534

bin/background_jobs

-#!/bin/sh
+#!/bin/bash
 
 cd $(dirname $0)/..
 

bin/background_jobs_sk

-#!/bin/sh
+#!/bin/bash
 
 cd $(dirname $0)/..
 app_root=$(pwd)

bin/background_jobs_sk_cluster

-#!/bin/sh
+#!/bin/bash
 
 cd $(dirname $0)/..
 app_root=$(pwd)