Description of problem:
When an image is mirrored to OCP 3.7 or OCP 3.9 clusters, and then it is migrated to a 4.6 cluster, the image's tag is not migrated.

Version-Release number of selected component (if applicable):
CAM 1.3.1
SOURCE CLUSTER: OCP 3.9 AWS (in 3.7 it happens too)
TARGET CLUSTER: OCP 4.6


How reproducible:
Always


Steps to Reproduce:
1. Create a namespace

oc new-project bz-test

2. Create a SA in this namespace

oc create sa mirror-sa -n bz-test

3. Give this account internal registry permissions

oc adm policy add-cluster-role-to-user registry-editor -z mirror-sa

4. Run this pod to mirror mysql 5.7 from openshift namespace to your current bz-test namespace

cat << EOF | oc create -f -
apiVersion: v1
kind: Pod
metadata:
  name: mirrorer
  namespace: bz-test
spec:
  containers:
  - args:
    - 'set -x; echo ''{"auths": {"''\${INTERNAL_REGISTRY}''": { "auth": "''\$(echo -n \$(oc whoami | sed ''s/.*://'')":"\$(oc whoami -t) | base64 -w 0)''"}}}'' > /tmp/config;
       oc image  mirror \${SOURCE_IMAGE} \${INTERNAL_REGISTRY}/\${TARGET_IMAGE} --insecure=true --registry-config=/tmp/config --force=true;'
    command:
    - /bin/sh
    - -c
    - --
    env:
    - name: INTERNAL_REGISTRY
      value: docker-registry.default.svc:5000
    - name: SOURCE_IMAGE
      value: docker-registry.default.svc:5000/openshift/mysql:5.7
    - name: TARGET_IMAGE
      value: bz-test/mysql:mirrored
    image: quay.io/sregidor/oc44:latest
    imagePullPolicy: Always
    name: podtest
  restartPolicy: OnFailure
  serviceAccountName: mirror-sa

EOF


5. Check that the image have been mirrored
$ oc get is -n bz-test
NAME      DOCKER REPO                                      TAGS       UPDATED
mysql     docker-registry.default.svc:5000/bz-test/mysql   mirrored   14 seconds ago

$ oc get istag -n bz-test 
NAME             DOCKER REF                                                                                                                UPDATED
mysql:mirrored   registry.access.redhat.com/rhscl/mysql-57-rhel7@sha256:9a781abe7581cc141e14a7e404ec34125b3e89c008b14f4e7b41e094fd3049fe   30 seconds ago


6. Migrate the bz-test namespace to the 4.6 cluster



Actual results:
In the target cluster we find that the image has been migrated, but the tag has not been migrated.

$ oc get is
NAME    IMAGE REPOSITORY                                                 TAGS   UPDATED
mysql   image-registry.openshift-image-registry.svc:5000/bz-test/mysql          

$ oc get istag -n bz-test
No resources found in bz-test namespace.



Expected results:
The image and the tag should be migrated.

Additional info:

This does not happen in OCP versions higher than 3.9. In OCP 3.10+ the migration works as expected.