Change env to bash to resolve Illegal option

What does this MR do?

After testing on some environment the script fails to due to the /bin/sh environment with the error below

Why was this MR needed?

To fix the script to default to the bash environment

./clear-docker-cache: 8: set: Illegal option -o pipefail

What's the best way to test this MR?

The script should run without any error