Set lock credenitals for showWhenLocked tests

On certain devices (i.e. auto), the lockscreen will not show unless a
secure screen lock is set. Withouth the lockscreen, split activities
will always be resumed regardless of their configuration (since the lock
screen is never showing), causing test failures.

Bug: 204513937
Test: atest android.server.wm.SplitActivityLifecycleTest (on
gcar_emu_x86 and sdk_gphone_x86)

Change-Id: Ia8a6cb444324a350a5a0e69eae872d304f8812fc
1 file changed