Fixed some bugs with main/side stage splits

- Dragging to right to dismiss no working.
- Dragging to left to dismiss closes all apps
- Not able to put app in split after left drag to dismiss
- Pressing back on last activity in one split dismisses both.
- Don't move home task forward when startActivityFromRecents with launch
root set.

Fixes: 176061049
Test: they pass!
Change-Id: Ic1219b747e995ee8833b31433356bd44435118da