navigation: don't run gesture animation if gestures are not enabled

Makes the animation when using 3 button navigation be closer to what we
have in non fallback mode, also fixing the problem when fallback recents
just started and don't have any views.

Fix 194487871
Test: manual with gestures, 2 button and 3 button nav

Change-Id: If3925d6bef1d14f51b86169d06607786972f5f1f
(cherry picked from commit 8d49c4bb)