Fix AzureRM state backend Azure CLI support

[Korijn]

I've been trying to use the azurerm state backend with Azure CLI to no avail with terraform v0.11.13.

I've documented my conclusions on a related issue in #18325 (comment)

After more investigation and some git blame commands, I've traced down the introduction of the problem to PR #19465

The PR simply toggles the feature flag for Azure CLI support, relying on the implementation of github.com/hashicorp/go-azure-helpers/authentication which has proven its worth in the azure terraform provider.

However, there is a (legacy?) dragon lurking in the code in the form of the following if-statement:

	if config.AccessKey == "" && config.SasToken == "" && config.ResourceGroupName == "" {	
		return fmt.Errorf("Either an Access Key / SAS Token or the Resource Group for the Storage Account must be specified")	
	}

This if-statement prevents usage of the Azure CLI as an authentication method, since in that case you would only provide the storage_account_name, container_name and key. That obviously does not satisfy the above condition.

I can't find any evidence that the changes in that PR were verified/tested manually, and there also aren't any automated tests that cover Azure CLI usage with the azurerm state backend.

I'm inclined to think the if-statement should simply be removed. All tests still pass after removing it.

Disclaimer: I would like to add a unit test to cover Azure CLI usage for the future, but I'm too much of a golang noob to actually be able to do it. Any help would be appreciated.

[hashicorp-cla]

All committers have signed the CLA.

[Korijn]

Sorry, this PR was completely misinformed. The problems I was experiencing have nothing to do with this change.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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