frameworks/base: Fix race conditions on resume/suspend using power key

The wakelock PowerManagerService.Display sometimes cannot be released
after two quick power key pressings like a double click during phone
sleep (the target will resume then supposedly suspend shortly).

The second key event disturbs display power state on resume, as a
result display resources won't get released on suspend, which is fixed
in this change.

CRs-Fixed: 566059
Change-Id: I633fd377ab235f203ebfb649a74449a2385740c4