Clear identity when releasing display resources.

We already do this in `close()` but not in `onVirtualDisplayRemoved()`.
This causes a security exception due to missing `WAKE_LOCK` permission
on builds that use HSUM.

Bug: 286185979
Test: presubmit
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ebaeb04cc8320ce15de9983d4c659571cd3b41dc)

Change-Id: I40447a461409fb523be3932d67b1fc6f0843e9e9