Disallow animating when opening home

Since this might trigger a minimizing home animation, this is
going to cause the stack clip to animate during the app
transition, leading to an issue where the primary stack isn't
cropped correctly in this transition.

Test: go/wm-smoke
Test: Split screen, go home, open assistant, do some action, press
home
Test: Same but open a 2ndary app that's not home
Fixes: 77675425

Change-Id: I4ac92337fe2140406ba962f6b1da1f18de5d3a56