Fix minimized state messup

We didn't dispatch the change, but still set the field. This lead to
issues where SysUI disagreed on the minimized state. To fix this, we
only check for state changes if the docked stack is visible, but then
dispatch the change always.

Bug: 28445644
Change-Id: Ie460135049c78e11c97f3160994ca4069bf82e6c