Send "Unlock to continue" bouncer message

On the user switcher bouncer, when "Manage Users" is
tapped, ensure a secondary message is displayed to
prompt the user to unlock.

Fixes: 365574398
Test: manual, use bouncer user switcher and tap manager users
Flag: EXEMPT bugfix
Change-Id: I4d9c0072576dce80dc23a18140ba41c5350ab6d4