Check animation is finished on hide

[carloscabanero]

Fixes hide - show - hide race condition, holding the HUD on screen. Call "done" only when the animation has finished as the show cycle could have been restarted.

Steps to reproduce:

• Create a single instance of the HUD for your notifications.
• Show and hide animated with a timer.
• Call another show/hide cycle again right when the hide animation is taking place.
• The HUD will hold on screen and never disappear.

This is an easy fix although it was difficult to pinpoint. On Blink Shell we use MBProgressHUD as a way to show changes between terminals. We change the content of the HUD instead of creating a new instance, and a new show-hide cycle must start.

Thanks!

[matej]

Sorry for taking so long to get to this.

I'm afraid this change might lead to a different issue - one that was solved in 5ec046a by @yas375. We need a solution that would work in both cases.