Batch Pool does not support private org dockerhub repositories

#### Problem Description
Azure batch integration with dockerhub repositories during pool creation works as expected for public repositories (both **user** based and **org** based, but not for **org** private repositories. I have also confirmed that private repository connections work as expected when the target private repository is under the **user** dockerhub account, and the exact **user** login credentials are provided.

However, private dockerhub connections do not work as expected for **organization** based private repositories, where member dockerhub login credentials are provided.

#### Steps to Reproduce
Azure Batch --> Add Pool
Image Type: Marketplace
Publisher: microsoft-azure-batch
Offer: ubuntu-server-container
Sku: 20-04-lts
Container Configuration:
- Container image names: XXXXXXXXXX
- Registry username: XXXXXX
- Password: XXXXXX
- Registry server: index.docker.io

#### Expected Results
Idle State for VM node upon Pool creation

#### Actual Results
Message - pull access denied for XXXXXXXX, repository does not exist or may require 'docker login': denied: requested access to the resource is denied

#### Additional Comments
Further confirmations:
- Confirmed dockerhub member access credentials are correct for the private repo housed under organization (confirmed via `docker login` and `docker pull...`
- Confirmed dockerhub organization is correctly allowing read access to desired dockerhub team members.
- Confirmed org repository when converted to public, works as expected on Azure Batch
- Confirmed that simply converting org repository to private results in Pool errors on Azure Batch
I have confirmed that if I make this repository named XXXXX when designates as public works as expected when creating a pool (even with registry username and password already specified). However, converting this repository to private, causes the error stated above.