Actually wait until the display is ready.

Actually wait until the display is ready.

When this was rewritten to only wait for display state changes and not
brightness changes, it forgot to take into account whether a change was
already in flight when reporting whether a change was happening. Fix
that so the display appropriately reports when it's ready and when it's
blocked.

Bug: 32559368
Test: Take systrace of device wakeup, see it actually waits until the
      display is actually ready

Change-Id: Ie3bd5c48d109a0fb2628ccc8f67bb52be51fad5c
(cherry picked from commit 640666fcfd4f40ba69dbe459adea7b31407209ac)