OCPBUGS-29469: fix Azure API SKU calls timing out - part 2

I erroneously assumed that Azure was not returning context errors but
that was not actually the case. It was happening as a result of the way
we structured the API call:

```
for page, err := client.List(ctx); page.NotDone(); err =
page.NextWithContext(ctx) {
    if err != nil {
	return nil, fmt.Errorf("failed to list SKUs: %w", err)
    }
}
```

If the `client.List` call fails (e.g, context deadline, auth error),
`page.NotDone()` will return `false` and we'll never enter the `for`
loop to check for `err`. Instead, we should make the `List` call and
check for error *before* entering the loop.

Author: r4f4

pkg/asset/installconfig/azure/client.go

@@ -180,7 +180,14 @@ func (c *Client) GetDiskSkus(ctx context.Context, region string) ([]azsku.Resour
 
 	var sku []azsku.ResourceSku
 
-	for skuPage, err := client.List(ctx); skuPage.NotDone(); err = skuPage.NextWithContext(ctx) {
+	// This has to be initialized outside the `for` because we need access to
+	// `err`. If initialized in the loop and the API call fails right away,
+	// `page.NotDone()` will return `false` and we'll never check for the error
+	skuPage, err := client.List(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list SKUs: %w", err)
+	}
+	for ; skuPage.NotDone(); err = skuPage.NextWithContext(ctx) {
 		if err != nil {
 			return nil, fmt.Errorf("error fetching SKU pages: %w", err)
 		}
@@ -197,12 +204,6 @@ func (c *Client) GetDiskSkus(ctx context.Context, region string) ([]azsku.Resour
 		return sku, nil
 	}
 
-	// Azure does not return an error in case of context deadline, so we need
-	// to check it ourselves
-	if err := ctx.Err(); err != nil {
-		return nil, fmt.Errorf("failed to list SKUs: %w", err)
-	}
-
 	return nil, fmt.Errorf("no disks for specified subscription in region %s", region)
 }
 
@@ -228,7 +229,11 @@ func (c *Client) ListResourceIDsByGroup(ctx context.Context, groupName string) (
 	defer cancel()
 
 	var res []string
-	for resPage, err := client.ListByResourceGroup(ctx, groupName, "", "", nil); resPage.NotDone(); err = resPage.NextWithContext(ctx) {
+	resPage, err := client.ListByResourceGroup(ctx, groupName, "", "", nil)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list resources: %w", err)
+	}
+	for ; resPage.NotDone(); err = resPage.NextWithContext(ctx) {
 		if err != nil {
 			return nil, fmt.Errorf("error fetching resource pages: %w", err)
 		}
@@ -248,7 +253,14 @@ func (c *Client) GetVirtualMachineSku(ctx context.Context, name, region string)
 	ctx, cancel := context.WithTimeout(ctx, 2*time.Minute)
 	defer cancel()
 
-	for page, err := client.List(ctx); page.NotDone(); err = page.NextWithContext(ctx) {
+	// This has to be initialized outside the `for` because we need access to
+	// `err`. If initialized in the loop and the API call fails right away,
+	// `page.NotDone()` will return `false` and we'll never check for the error
+	page, err := client.List(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("failed to list SKUs: %w", err)
+	}
+	for ; page.NotDone(); err = page.NextWithContext(ctx) {
 		if err != nil {
 			return nil, fmt.Errorf("error fetching SKU pages: %w", err)
 		}
@@ -270,12 +282,6 @@ func (c *Client) GetVirtualMachineSku(ctx context.Context, name, region string)
 		}
 	}
 
-	// Azure does not return an error in case of context deadline, so we need
-	// to check it ourselves
-	if err := ctx.Err(); err != nil {
-		return nil, fmt.Errorf("failed to list SKUs: %w", err)
-	}
-
 	return nil, nil
 }
 
@@ -392,7 +398,11 @@ func (c *Client) GetLocationInfo(ctx context.Context, region string, instanceTyp
 
 	// Only supported filter atm is `location`
 	filter := fmt.Sprintf("location eq '%s'", region)
-	for res, err := client.List(ctx, filter, "false"); res.NotDone(); err = res.NextWithContext(ctx) {
+	res, err := client.List(ctx, filter, "false")
+	if err != nil {
+		return nil, fmt.Errorf("failed to list SKUs: %w", err)
+	}
+	for ; res.NotDone(); err = res.NextWithContext(ctx) {
 		if err != nil {
 			return nil, err
 		}