ActivityThread: Throw an exception back to caller when supposed to

this dirt snuck in with halo.

Change-Id: I8f6ad0f55d135449eb08afc073fe4b3a23ebf4cf
Halo and MultiWindow Tweaks

1. Add halo state check, multiwindow will not cast on if halo exist.
2. Recent panel popup menu: hide multiwindow option if halo exist
3. If HALO is activated all HALO notifications will open in floating window mode.
   If HALO is not activated notifications will open in mutiwimdow mode.