Fix external_url property to pull in real ENV value
Fix external_url property to pull in real ENV value

cloudfoundry-incubator/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,erjohnso/bosh-google-cpi-release,evandbrown/bosh-google-cpi-release,cloudfoundry-incubator/bosh-google-cpi-release