Improve savanna keystone auth configuration

We're doing to use common keystone configuration approach - section
keystone_authtoken with config opts from the python-keystoneclient
auth_token middleware.

Change-Id: Ibbe0c76ee3b00045f5cb5134bd7661e9cef6ccdd
Perform safety checks in create-stack-user.sh

This adds some safety checks to the stack user creation script.

This includes:
- Using set -o errexit to exit early on errors
- Make sure STACK_USER is set before doing anything with it

Change-Id: If027daddd03e32c5ba3c2ebb05ad5b27d2868b0a
Merge "Perform safety checks in create-stack-user.sh"
Merge "Improve savanna keystone auth configuration"