Add back clear tag to smoke-testNuGet.Config

Author: dseefeld

smoke-testNuGet.Config

@@ -1,6 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
   <packageSources>
+    <!--To inherit the global NuGet package sources remove the <clear/> line below -->
+    <clear />
     <add key="source-built-packages" value="SOURCE_BUILT_PACKAGES" />
     <add key="api.nuget.org" value="https://api.nuget.org/v3/index.json" />
     <add key="dotnet-core" value="https://dotnetfeed.blob.core.windows.net/dotnet-core/index.json" />