Fix for async await suspend-resume mechanics

[rogeralsing]

Hotfix for async await suspend-resume mailbox mechanics.

[rogeralsing]

cc @nvivo

There is really no excuse for this one, we rushed the v1 release.
The code failed whenever more than one message was sent to a async suspended actor.

We do have a test for this

public class SuspendActor : ReceiveActor
    {
        public SuspendActor()
        {
            var state = 0;
            Receive<string>(s => s == "change", _ =>
            {
                state = 1;
            });
            Receive<string>(AsyncBehavior.Suspend, async _ =>
            {
                Self.Tell("change");
                await Task.Delay(TimeSpan.FromSeconds(1));
                //we expect that state should not have changed due to an incoming message
                Sender.Tell(state);
            });
        }
    }

Can anyone spot the issue?
async methods in C# are really not async until they hit await so the Self.Tell("change") fired before the mailbox was suspended, thus making the test pass.

In general, I think we have been too sloppy on the test coverage side of things lately.

[nvivo]

Thanks!

[Aaronontheweb]

There is really no excuse for this one, we rushed the v1 release.There is really no excuse for this one, we rushed the v1 release.

We had several weeks to find this bug from the time the PR was accepted to when the NuGet package was pushed. The release was definitely not rushed. But bugs happen - not a big deal. Don't turn it into a fault-finding mission.