Fix for trx beautifier (microsoft#1709)

Author: abhishkk

src/Microsoft.TestPlatform.Extensions.TrxLogger/TrxLogger.cs

@@ -379,7 +379,7 @@ internal virtual void PopulateTrxFile(string trxFileName, XmlElement rootElement
 
                 using (var fs = File.Open(trxFileName, FileMode.Create))
                 {
-                    using (XmlWriter writer = XmlWriter.Create(fs, new XmlWriterSettings { NewLineHandling = NewLineHandling.Entitize }))
+                    using (XmlWriter writer = XmlWriter.Create(fs, new XmlWriterSettings { NewLineHandling = NewLineHandling.Entitize, Indent = true }))
                     {
                         rootElement.OwnerDocument.Save(writer);
                         writer.Flush();