Dismiss docked stack when ShowWhenLocked activity is over keyguard (1/2)

Activities with ShowWhenLocked flag when docked should dismiss the
docked stack and appear after screen turns back on. This incorporates
missing code from ag/1013634 that was missed during refactoring.

Fixes: 36166079
Test: run-test CtsServicesHostTestCases
android.server.cts.KeyguardTests#testShowWhenLockedActivityWhileSplit
Change-Id: I003cdd0be46fe6b9640e2bfbfca582150f2723b7