Bug 1475868

Description of problem:
At this time if one needs to add a CA to the default trust store of an image, they would need to build the image running. 

For example if a user needs to add a Trusted CA to the docker registry for proxy pulls they would need to rebuild the image to add the ca to the image. 

```
$ cp ca.cert your_internalCA.crt
$ cat > /tmp/dockerfile << EOF 
FROM openshift3/ose-docker-registry
USER root
ADD your_internalCA.crt /etc/pki/ca-trust/source/anchors
RUN /bin/update-ca-trust
USER 1001
EOF
$ cd /tmp
$ sudo docker build ./ -t ExternalRegistryURL:openshift3/ose-docker-registry-custom:latest
$ sudo docker push ExternalRegistryURL:openshift3/ose-docker-registry-custom:latest

Then change the DC of the registry, changing the image to point to the image that was created: 
# oc edit dc docker-registry
```

Looking for a way to provide a secret to an image that would automatically add the CA data to the catrust for OpenShift image.