base

Fixing notification of the docked stack state for the current user.

- When there are multiple users, ensure that we check that there are
  tasks in the docked stack for each user (instead of just the presence
  of the docked stack) and re-notify listeners of the state of the
  docked stack when the user is switched.

Change-Id: I911c4a32db187f9cd29d462309bd0cf7febb1993