Recent GCI e2e test failures suggest that the image name was double quoted when
passed to gcloud. E.g.,
```
09:59:51 - Invalid value for field
'resource.disks[0].initializeParams.sourceImage':
'https://www.googleapis.com/compute/v1/projects/container-vm-image-staging/global/images/"gci-base-53-8530-36-0"'.
The referenced image resource cannot be found.
```
The `-r`, or `--raw-output` option strips quotes from jq's output. With this
change, the output looks like:
```
+ export KUBE_GCE_MASTER_IMAGE=gci-base-54-8650-0-0 # Not quoted
```
e4cfb91bd9