Fix test TestAccIotHubDPS_linkedHubs

[myc2h6o]

connection_string is not referencing existing IoT Hubs, causing error "Unable to find the IoThub ...", fixing it by using existing reference.

[myc2h6o]

Test result

[katbyte]

test failure, perhapes we need to poll/wait on creation?

------- Stdout: -------
=== RUN   TestAccIotHubDPS_linkedHubs
=== PAUSE TestAccIotHubDPS_linkedHubs
=== CONT  TestAccIotHubDPS_linkedHubs
    testcase.go:110: Step 1/4 error: Error running apply: exit status 1
        
        Error: creating/updating IoT Device Provisioning Service Iot Hub Dps: (Provisioning Service Name "acctestIoTDPS-220829185508492455" / Resource Group "acctestRG-220829185508492455"): iothub.IotDpsResourceClient#CreateOrUpdate: Failure sending request: StatusCode=404 -- Original Error: Code="Failed" Message="The async operation failed." InnerError={"unmarshalError":"json: cannot unmarshal number into Go struct field serviceErrorInternal.code of type string"} AdditionalInfo=[{"code":404002,"httpStatusCode":"NotFound","message":"Unable to find the IoThub `acctestIoTHub2-220829185508492455.azure-devices.net`. Check if the hub exists and the connection information is correct. If you contact a support representative please include this correlation identifier: ef2c3d4b-cd68-4a92-a2a8-4142e277a8f3, timestamp: 2022-08-29 18:58:55Z, errorcode: IH404002."}]
        
          with azurerm_iothub_dps.test,
          on terraform_plugin_test.tf line 61, in resource "azurerm_iothub_dps" "test":
          61: resource "azurerm_iothub_dps" "test" {
        
--- FAIL: TestAccIotHubDPS_linkedHubs (338.94s)
FAIL

[myc2h6o]

@katbyte thanks for reviewing the change! I've done some test locally and this issue does happen sometimes. I tried looking at the resource properties, and they are all same during the provisioning failure time whether the issue happens or not, and a retry can create the IotHub DPS correctly. Fortunately, the error code is 404 for this specific issue that linked hubs are not found, I'll add a poll and retry to check the 404 error.

[katbyte]

LGTM 🎩

[github-actions]

This functionality has been released in v3.21.0 of the Terraform Provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template. Thank you!

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.