fix getblobcontent issue when length is -1

Author: yifanz7

src/Storage/Storage/Blob/Cmdlet/CopyAzureStorageBlob.cs

@@ -321,7 +321,6 @@ private void CopyBlobSync(IStorageBlobManagement destChannel, string srcUri, str
         private async Task CopyFromUri(long taskId, IStorageBlobManagement destChannel, Uri srcUri, BlobBaseClient destBlob)
         {
             bool destExist = true;
-            //Track2Models.BlobType? destBlobType = Util.GetBlobType(destBlob);
             Track2Models.BlobType? srcBlobType = Util.GetBlobType(new BlobBaseClient(srcUri, ClientOptions), true).Value;
             Track2Models.BlobType? destBlobType = Util.GetBlobType(new BlobBaseClient(srcUri, ClientOptions), true).Value;
             Track2Models.BlobProperties properties = null;

src/Storage/Storage/Blob/Cmdlet/GetAzureStorageBlobContent.cs

@@ -150,6 +150,13 @@ internal virtual async Task DownloadBlob(long taskId, IStorageBlobManagement loc
             string activity = String.Format(Resources.ReceiveAzureBlobActivity, blob.Name, filePath);
             string status = Resources.PrepareDownloadingBlob;
             ProgressRecord pr = new ProgressRecord(OutputStream.GetProgressId(taskId), activity, status);
+
+            // Get the length information if the blob doesn't have it 
+            if (blob.Properties.Length < 0)
+            {
+                blob.FetchAttributes();
+            }
+
             DataMovementUserData data = new DataMovementUserData()
             {
                 Data = blob,