Fixed bash script to use workspace_dir instead of working_dir
Fixed bash script to use workspace_dir instead of working_dir

[#113382709](https://www.pivotaltracker.com/story/show/113382709)

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