More cleanup of Elmah (#6429)

Clean Elmah

Author: cristinamanum

src/NuGetGallery.Core/Infrastructure/TableErrorLog.cs

@@ -190,6 +190,12 @@ public override string Log(Error error)
 
             private void Obfuscate(Error error)
             {
+                error.User = string.Empty;
+                if (error.Form != null)
+                {
+                    error.Form.Clear();
+                }
+
                 //ServerVariables overrides requiring context from the http request should be handled in NuGetGallery.QuietLog
                 var elmahException = error.Exception as ElmahException;
                 if (elmahException != null)