Missing permission "Microsoft.Compute/availabilitySets/delete" for the Required permissions for creating compute resources in 

https://docs.openshift.com/container-platform/4.15/installing/installing_azure/installing-azure-account.html 

Without this permission when deleting machine in region without zone, report error:
machine/machineset-25436-jw6wl DeleteError: failed to delete machine "machineset-25436-jw6wl": failed to delete availability set: failed to delete availability set ci-op-84s06zk8-97600-8c84v_machineset-25436-as: compute.AvailabilitySetsClient#Delete: Failure responding to request: StatusCode=403 -- Original Error: autorest/azure: Service returned an error. Status=403 Code="AuthorizationFailed" Message="The client '6c7a9fe1-0b40-4a89-976a-2fad27da9092' with object id '6c7a9fe1-0b40-4a89-976a-2fad27da9092' does not have authorization to perform action 'Microsoft.Compute/availabilitySets/delete' over scope '/subscriptions/53b8f551-f0fc-4bea-8cba-6d1fefd54c8a/resourceGroups/ci-op-84s06zk8-97600-8c84v-rg/providers/Microsoft.Compute/availabilitySets/ci-op-84s06zk8-97600-8c84v_machineset-25436-as' or the scope is invalid. If access was recently granted, please refresh your credentials." (15 times) 

Add "Microsoft.Compute/availabilitySets/delete" to the Required permissions for creating compute resources in https://docs.openshift.com/container-platform/4.15/installing/installing_azure/installing-azure-account.html