Update the initial bouncer message whenever the security mode changes

Flag: ACONFIG com.android.systemui.revamped_bouncer_messages NEXTFOOD
Test: After first boot, setup a PIN. From the lockscreen,
bring up the primary bouncer and observe the "Enter PIN" message.
Fixes: 336337248
Test: atest BouncerMessageInteractorTest

Change-Id: I0145b38ede1b3eed105952c52b641cea99d65e32