InvokeAsync does not finally check CancellationToken

[HenKun]

In contrast to the other overloads, InvokeAsync in

winforms/src/System.Windows.Forms/src/System/Windows/Forms/Control_InvokeAsync.cs

Line 244 in 0ce1218

try

does not check the cancellationToken before finally invoking the delegate.

This should be done in order to

• be consistent
• avoid an unnecessary invocation

[kirsan31]

Here was some comments about InvokeAsync implementation (including cancellationToken). Didn't checked it by myself.