Description of problem:
Per https://github.com/openshift/builder/issues/71, when the the image policy defined in images.config.openshift.io/cluster whitelists the set of registries from which we're allowed to push images, the generated policy.json defaults to disallowing all transports, which prevents the builder from committing or pushing a new image.

Version-Release number of selected component (if applicable):
4.1.0-rc.0

How reproducible:
Always

Steps to Reproduce:
1. Set a cluster spec of:
  allowedRegistriesForImport:
  - domainName: registry.redhat.io
    insecure: false
  - domainName: quay.io
    insecure: false
  - domainName: registry.access.redhat.com
    insecure: false
  registrySources:
    allowedRegistries:
    - registry.redhat.io
    - registry.access.redhat.com
    - image-registry.openshift-image-registry.svc:5000
    - quay.io
  allowedRegistriesForImport:
  - domainName: registry.redhat.io
    insecure: false
  - domainName: quay.io
    insecure: false
  - domainName: registry.access.redhat.com
    insecure: false
  registrySources:
    allowedRegistries:
    - registry.redhat.io
    - registry.access.redhat.com
    - image-registry.openshift-image-registry.svc:5000
    - quay.io
2. Start a build.

Actual results:
The generated policy.json looks like:
{"default":[{"type":"reject"}],"transports":{"atomic":{"image-registry.openshift-image-registry.svc:5000":[{"type":"insecureAcceptAnything"}],"quay.io":[{"type":"insecureAcceptAnything"}],"registry.access.redhat.com":[{"type":"insecureAcceptAnything"}],"registry.redhat.io":[{"type":"insecureAcceptAnything"}]},"docker":{"image-registry.openshift-image-registry.svc:5000":[{"type":"insecureAcceptAnything"}],"quay.io":[{"type":"insecureAcceptAnything"}],"registry.access.redhat.com":[{"type":"insecureAcceptAnything"}],"registry.redhat.io":[{"type":"insecureAcceptAnything"}]}}}

The build fails with:
error: build error: error copying layers and metadata for container "ceed796969e4947a471e4c866606d1fb5067055f7c0d8d9e3b174e3906fa37d7": Source image rejected: Running image containers-storage:ruby-working-container is rejected by policy.

Expected results:
Regardless of the spec, the builder should not fail to commit an image, or push an image because local storage is not mentioned in the policy.json.