Fix schema not always visibile just after creation.

Retry client.Get in resourceApiManagementApiSchemaCreateUpdate in case that
schema was not yet created.

azurerm/internal/services/apimanagement/api_management_api_schema_resource.go

@@ -103,15 +103,23 @@ func resourceApiManagementApiSchemaCreateUpdate(d *pluginsdk.ResourceData, meta
 		return fmt.Errorf("creating or updating API Schema %q (API Management Service %q / API %q / Resource Group %q): %s", schemaID, serviceName, apiName, resourceGroup, err)
 	}
 
-	resp, err := client.Get(ctx, resourceGroup, serviceName, apiName, schemaID)
+	err := pluginsdk.Retry(d.Timeout(pluginsdk.TimeoutCreate), func() *pluginsdk.RetryError {
+		resp, err := client.Get(ctx, resourceGroup, serviceName, apiName, schemaID)
+		if err != nil {
+			if utils.ResponseWasNotFound(resp.Response) {
+				return pluginsdk.RetryableError(fmt.Errorf("Expected schema %q (API Management Service %q / API %q / Resource Group %q) to be created but was in non existent state, retrying", schemaID, serviceName, apiName, resourceGroup))
+			}
+			return pluginsdk.NonRetryableError(fmt.Errorf("Error geting schema %q (API Management Service %q / API %q / Resource Group %q): %+v", schemaID, serviceName, apiName, resourceGroup, err))
+		}
+		if resp.ID == nil {
+			return pluginsdk.NonRetryableError(fmt.Errorf("Cannot read ID for API Schema %q (API Management Service %q / API %q / Resource Group %q): %s", schemaID, serviceName, apiName, resourceGroup, err))
+		}
+		d.SetId(*resp.ID)
+		return nil
+	})
 	if err != nil {
-		return fmt.Errorf("retrieving API Schema %q (API Management Service %q / API %q / Resource Group %q): %s", schemaID, serviceName, apiName, resourceGroup, err)
-	}
-	if resp.ID == nil {
-		return fmt.Errorf("Cannot read ID for API Schema %q (API Management Service %q / API %q / Resource Group %q): %s", schemaID, serviceName, apiName, resourceGroup, err)
+		return fmt.Errorf("Error geting schema %q (API Management Service %q / API %q / Resource Group %q): %+v", schemaID, serviceName, apiName, resourceGroup, err)
 	}
-	d.SetId(*resp.ID)
-
 	return resourceApiManagementApiSchemaRead(d, meta)
 }