azure: move the .vhd extension logic to the callers

It always felt wrong that the method uploaded the blob under a different name
than the one specified in the blob metadata.

This commit moves the responsibility of specifying the right extension to
the callers. azure.EnsureVHDExtension helper was added to simplify this.

Signed-off-by: Ondřej Budai <ondrej@budai.cz>

cmd/osbuild-upload-azure/main.go

@@ -43,10 +43,12 @@ func main() {
 		os.Exit(1)
 	}
 
+	blobName := azure.EnsureVHDExtension(path.Base(fileName))
+
 	err = c.UploadPageBlob(
 		azure.BlobMetadata{
 			StorageAccount: storageAccount,
-			BlobName:       path.Base(fileName),
+			BlobName:       blobName,
 			ContainerName:  containerName,
 		},
 		fileName,