Strange behavior from entity focus/inspect tool/window

From #3061:

> However, I did notice some funky behavior when using the "focus"/"inspect" tool; I managed to get things into a state such that, if the code above hid the object, Cesium would render some other fixed representation (like, it had cached one of the states and would always show that). I can make a new bug report with a video of this if you like.

I'm not entirely sure the intended behavior of this tool, but whatever is going on here definite seems wrong. It always happens when I run this code. The strange select behavior seems to be because of the added code (that changes the material and visibility); I tried wrapping it in a `setTimeout`, but it doesn't look like that worked for the video capture.

[focus.bug.hevc.mkv.zip](https://github.com/AnalyticalGraphicsInc/cesium/files/539169/focus.bug.hevc.mkv.zip)

Start with the attached focus.bug.hevc.mkv.zip and reproduce the focus/inspect sequence described in the issue, including changes to material and visibility. No source files, tests, or entry points are named; done means the intended behavior is clarified and the incorrect cached representation no longer appears.

Written by the indexing model from the issue text.