Port ForbidAsync changes to 2.0.x

[jkotalik]

See #917 and #918

[Eilon]

This patch bug is approved for the 2.0.x patch. Please send a PR to the feature/2.0.1 branch and get it reviewed and merged. When we have the rel/2.0.1 branches ready please port the commit to that branch.

[Eilon]

@jkotalik / @HaoK / @Tratcher - Do we need to consider any quirks mode switch here? Is it even remotely possible that anyone would be relying on the 2.0.0-rtm behavior?

[Tratcher]

No, Forbid already falls back to Challenge if not set.

[natemcmaster]

Looks like this was fixed in #939, right @jkotalik ?

[jkotalik]

Yes we did!

[Eilon]

Hi, we have a public test feed that you can use to try out the ASP.NET/EF Core 2.0.3 patch!

To try out the pre-release patch, please refer to the following guide:

• ASP.NET/EF Core 2.0.3 patch pre-release test feed Announcements#274 (info)
• ASP.NET/EF Core 2.0.3 patch pre-release test feed - discussion dotnet/aspnetcore#2254 (discussions and questions)

We are looking for feedback on this patch. We'd like to know if you have any issues with this patch by updating your apps and libraries to the latest packages and seeing if it fixes the issues you've had, or if it introduces any new issues. If you have any issues or questions, please reply on this issue to let us know as soon as possible.

Thanks,
Eilon