SignOutAsync should take [] of AuthenticationSchemes

[Tratcher]

From @rustd on March 14, 2016 22:22

A user has to specify SignOut per authentication scheme as follows https://github.com/aspnet/Templates/blob/dev/src/Rules/StarterWeb/OrganizationalAuth/Single/Controllers/AccountController.cs#L24
With this change we will have the same code as in Katana

Copied from original issue: aspnet/Security#742

[Tratcher]

I don't think we need this, we had considered it as an intermediate design that didn't provide AuthProperties but opted for aspnet/Security#743 instead.

[kevinchalet]

The syntax in MVC would be much better if aspnet/Mvc#4259 was merged.

/cc @danroth27

[Tratcher]

@HaoK is this still relevant or can we close it? It looks like MVC is doing most of the work for us.

[aspnet-hello]

This issue was moved to dotnet/aspnetcore#2721