Description of problem:
oc adm catalog mirror does not work for target repo without subname

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[root@preserve-olm-env bin]# oc adm catalog mirror --manifests-only --to-manifests=./ quay.io/kuiwang/operators-dockerio:v1 registry.ocp-edge-cluster-0.qe.lab.redhat.com:5000
using database path mapping: /:/tmp/072428253
error: destination registry required
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it works for previous release, like 4.6
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[root@preserve-olm-env bin]# oc version
Client Version: 4.6.0-0.nightly-2020-12-21-163117

[root@preserve-olm-env bin]# oc adm catalog mirror --manifests-only --to-manifests=./ quay.io/kuiwang/operators-dockerio:v1 registry.ocp-edge-cluster-0.qe.lab.redhat.com:5000
using database path mapping: /:/tmp/081471900
wrote database to /tmp/081471900
using database at: /tmp/081471900/bundles.db
no digest mapping available for docker.io/atlasmap/atlasmap-operator:0.1.0, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/cluster-operator:0.11.1, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/operator:0.12.2, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/operator:0.13.0, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/operator:0.14.0, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/cluster-operator:0.11.0, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/strimzi/operator:0.12.1, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/atlasmap/atlasmap-operator:0.2.0, skip writing to ImageContentSourcePolicy
no digest mapping available for docker.io/tremolosecurity/myvd-k8s-operator:latest, skip writing to ImageContentSourcePolicy
wrote mirroring manifests to ./
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Version-Release number of selected component (if applicable):
[root@preserve-olm-env bin]# oc version
Client Version: 4.7.0-0.nightly-2020-12-21-131655
Server Version: 4.7.0-0.nightly-2020-12-21-131655
Kubernetes Version: v1.20.0+87544c5


How reproducible:
always

Steps to Reproduce:


Actual results:
can not mirror for registry.ocp-edge-cluster-0.qe.lab.redhat.com:5000 registry

Expected results:
can mirror for registry.ocp-edge-cluster-0.qe.lab.redhat.com:5000


Additional info: