Allow user `vali` to access stemcell.tgz
Allow user `vali` to access stemcell.tgz

Background is that the auto-update pipeline failed because the vali user did not have
permission to access the cpi-release.tgz

Also fixing minor shellcheck warnings

Co-authored-by: Max Becker <e6d855fe2263fd0035edb7e1f665a7466a1b4c9c@sap.com>

cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release,cloudfoundry-incubator/bosh-openstack-cpi-release