Unable to Import public Docker image

**Describe the bug**
I'm unable to import certain images from Docker Hub to Azure Container Registry using 'az acr import'

`Deployment failed. Correlation ID: 039d8a3f-5938-467f-b97d-5b5f403d6439. Operation registries-feeccf4f-0f04-11eb-aecd-0b70a1ccdcda failed. Resource /subscriptions/5170570b-48b6-414d-86b4-xxxxxxxxxx/resourceGroups/prod-rg-devtools/providers/Microsoft.ContainerRegistry/registries/prodacrelectool Invalid message Unauthorized Unauthorized {"errors":[{"code":"UNAUTHORIZED","message":"authentication required","detail":[{"Type":"repository","Class":"","Name":"library/axoniq/axonserver","Action":"pull"}]}]}`

**To Reproduce**
1. `az acr import --name prodacrelectool --source "docker.io/library/axoniq/axonserver:latest" --image "axoniq/axonserver:latest" --subscription "5170570b-48b6-414d-86b4-xxxxxxxxxx"`

However, for certain images, the import is successful, ie. 'python', 'hello-world' images:
`az acr import --name prodacrelectool --source "docker.io/library/python" --subscription "5170570b-48b6-414d-86b4-xxxxxxxxxx"` works fine.

The only difference I found so far that all the successful imports were 1.) using official images, 2.) from verified vendor 3.) the image names were not using slash.

**Expected behavior**
Successfully import any public images from Docker Hub

**Environment information**
- OS: Xubuntu 20.04 in VirtualBox
- Azure CLI version: 2.13.0
- Docker version: 19.03.13