Modify example to pass the GCE json key as a string and not a hash
Modify example to pass the GCE json key as a string and not a hash

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