Fix bouncer inflation race condition

For the multi-user bouncer only, the user switcher
and the security screen are inflated separately but
need to reference each other. After the security
screen is reinflated, such as after a display settings
change, pass the new reference back to the user
switcher.

Fixes: 335347904
Test: atest KeyguardSecurityContainerControllerTest
Test: manual continuously switch users
Test: manual update display settings and go back to
bouncer
Flag: EXEMPT bugfix

Change-Id: Ibb1d61305513b88aa3b9f7c0dd3755b7013b917c