Fix getting stuck when zooming

[nikakhov]

No description provided.

[hpinkos]

Thanks @nikakhov. Can you send us a Contributor Licence Agreement (CLA) so we can review this? You can find instructions here: https://github.com/AnalyticalGraphicsInc/cesium/blob/master/CONTRIBUTING.md#contributor-license-agreement-cla

[pjcozzi]

@nikakhov were you able to send in a CLA? Perhaps I missed it?

[nikakhov]

Let me share a few thoughts. Perhaps we are not yet at that point where this code should be merged. In the issue discussion, I mentioned how this fix is incomplete and needs to be supplemented with additional changes, such as setting minimum and maximum zoom limits.

[pjcozzi]

@nikakhov please open a new pull request when you think this is ready, thanks again for supporting Cesium.