Based on https://github.com/openshift/installer/pull/9718, installer default behavior is changed back to create user-assigned identity to avoid pulling image from ACR failed.

https://github.com/openshift/installer/pull/9625 removed the user-assigned identity configuration from Azure ARM template, so the issue also happens on UPI cluster.

The Azure ARM template in UPI installation doc is synced from installer repo automatically, #9625 needs to be reverted until installer default behavior changes to use "None" identity type, so that doc has correct ARM template content.   

    4.19+

    Always

    1. Create UPI install on 4.19+
    2. Pull image from ACR
    3.
    

    Failed to pull image from ACR

    Succeeded to pull image from ACR