Fix ordering of notifying dismiss callback

Otherwise all unlocks will result in onDismissCancelled.

Also fixes a race condition bug where we call
reportKeyguardShowingChanged but we don't wait until the state is
updated. Then, we called onDismissSucceeded such that
KeyguardManager.isDeviceLocked would still return true. Fix this
by waiting for the message to be processed.

Note that delays shouldn't be a problem here as we are soon
calling reportKeyguardShowingChanged from the UiOffloadThread.

Test: KeyguardLockedTests
Change-Id: I0b312a5f02be3a3d1028d8bf0cd1b8e6a33476ce
Fixes: 38219395