[Bouncer] Fix flicker tests.

Fixes an issue where dismissaction is set to null before it's called
when bouncer is unlocked.
Fixes an issue where we call updateState everytime expansion changes.
This was causing an overstack flow issue. Also it's super not performant
to call this everytime expansion changes.

Bug: 240298500
Test: Passed flicker tests for cts test. Passed presubmit.
Test: Tested showing the bouncer.
Test: Tested opening notification from lockscreen.
Change-Id: Iede30acdf11689c5da7abd2d5e5b4619aa10b34a