CSSTransition with transitions disabled end up with both -exit-done and -enter-done classes

[goffioul]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
When defining a CSSTransition component with both "enter" and "exit" set to false, the component ends up with both -exit-done and -enter-done classes after 2 transitions.

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem via https://jsfiddle.net or similar (template: https://jsfiddle.net/m4mb9Lg3/4/).
https://jsfiddle.net/5sLyLhyg/1/

What is the expected behavior?
Only one of the -exit-done and -enter-done should exist on the DOM node.

Which versions, and which browser / OS are affected by this issue? Did this work in previous versions?
Tested on Chrome 66 with react 16.2.0 and react-transition-group 2.3.1