Fix Launcher being occluded during rotate transition

I1177b1ef removed independent checks and reparent all transition-leashes
to root leash. Which result to wrong z-order setup during rotation
transition because it also reparents task display area transition-leash
to root leash.

This brings back independent change checks and overrides root task
targets with corresponding child task info. This is needed because
Launcher monitors leaf task id to perform recent apps transition.
Otherwise child task targets might get transformed twice with the flow
like RecentsView#redrawLiveTile.

Bug: 206487881
Test: close landscape app to portrait home, observed Launcher stays on
      top of wallpaper during transition.
Test: swipe up split pair to recent apps panel transformes thumbnail
      pair properly.

Change-Id: I234e329c40938cec7e35a62dc51d00cdf2e84b0b