Show recents when task moves to docked stack

When task was moved to docked stack using adb command,
recents didn't show and docked stack was minimized when
home task obtained focus.
This CL shows recents if needed when task is moved to
docked stack.

Bug: 28215216
Change-Id: If1cfb9d24bd77cc9c3c8fad3479f115d7aca1301