DO NOT MERGE Dont restore focus on new HUN window

When a HUN window shows for the first time, Android framework can try to
find a default focus. As such, the FPV may try to focus the topmost HUN
by default, without having nudged to the HUN window.

Bug: 175897692
Test: manual (reboot and trigger HUN via kitchen sink)
Change-Id: Id4008c587aea353dc0c441593fe32e6e9fea5463