nuget.exe on v3 service only uses credentials for request to index.json

[jmyersmsft]

We're seeing some strange auth issues here. Using:

• nuget.exe 3.1.0-beta downloaded from the link in the blog post, or NuGet.CommandLine.3.2-beta-10868 from nugetbuild feed on myget
• an authenticated v3 source
• credentials stored in nuget.config,

running:

nuget list -source MyAuthenticatedSource

gives the following behavior:

1. GET (index.json) (without credentials) -> 401 with auth challenge
2. GET (index.json) (with Basic credentials) -> 200
3. GET (SearchQueryService URL) (without credentials) -> 401 with auth challenge
4. NuGet.exe gives up with the message "Failed to retrieve metadata from source: '[query URL]'.". No further HTTP requests are issued,

index.json and the SearchQueryService are on the same host, if that's interesting

[feiling]

This is fixed by the fix of #1216