Toast: Fix JE caused by service not bind

Before calling unbindService, we need to call bindService,
but there are some logic problems in DisplayHashController,
which cause this problem to occur. Add the control variable mBound.

Bug: 232001919

Test: atest DisplayHashManagerTest

Signed-off-by: hupeng3 <hp121520@gmail.com>
Change-Id: I84cd1542af345d5078ef40ab282d2d405e967e8e