azurerm_storage_account - Fix acctest TestAccAzureRMStorageAccount_routing

[magodo]

Currently, the test case is failing like below:

This PR ensures the computed attributes related to routing are always set, which fixes the acctest TestAccAzureRMStorageAccount_routing.

Test

terraform-provider-azurerm on  storage_account_update via 🐹 v1.22.0 took 16s
💤  TF_ACC=1 go test -v -timeout=20h ./internal/services/storage -run='TestAccAzureRMStorageAccount_routing'
=== RUN   TestAccAzureRMStorageAccount_routing
=== PAUSE TestAccAzureRMStorageAccount_routing
=== CONT  TestAccAzureRMStorageAccount_routing
--- PASS: TestAccAzureRMStorageAccount_routing (247.23s)
PASS
ok      github.com/hashicorp/terraform-provider-azurerm/internal/services/storage       247.247s

[katbyte]

LGTM 🍔

[github-actions]

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