Steps to reproduce:
1. Open attached project
2. Open the main scene
3. Play the scene
4. Hold the left mouse button on Yes/No buttons
5. Move the mouse a few pixels while holding left mouse button and still being in the button area
6. Observe the button deselecting itself

Expected result: The button should still be selected when the left mouse button is held and cursor is moved in the button area
Actual result: The button deselects itself when the cursor held down is moved

Note: When the "Event Trigger" component is attached to a parent object of the buttons, the buttons of that parent object lose the ability to still be selected when the cursor is held down and moved. This does not appear to happen when there is no "Event Trigger" component attached.

Reproduced in: 2017.1.0a4, 5.6.0f2, 5.6.0f1, 5.5.2f1