Suppress flyout during mode switching

When switching from bubble bar to floating bubbles, suppress the
flyout so that it doesn't show again.

Flag: com.android.wm.shell.enable_bubble_bar
Fixes: 376310453
Test: manual
      - grab a felix
      - add a bubble to the bubble bar, and observe flyout
      - fold
      - observe that the flyout doesn't show again
Change-Id: I389be796ab2bb89f9b04756c121138360f075011