bugfix: 54418438: delete environment iso after vm is deleted
bugfix: 54418438: delete environment iso after vm is deleted

cloudfoundry-incubator/bosh-vcloud-cpi-release,cloudfoundry-incubator/bosh-vcloud-cpi-release,cloudfoundry-incubator/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release,wcamarao/bosh-vcloud-cpi-release