When auto mode is enabled and trees are painted on terrain, navigating in scene view restarts whole baking process

Steps for reproduction:
1) Download the project from case 955667
2) Open the scene `TestScene`
3) Start baking with auto mode enabled
4) Navigate in the scene view
5) Observe that baking restarts

Notes:
- Already fixed in 2017.3, the fix won't be backported to 2017.2
- Occurs with both baking backends
- Occurs regardless of `view prioritization` feature
- An image is attached below to demonstrate the problem