Use a blank splash screen for new task activity

Add a condition when launch activity from continuous package, consider
to show a blank splash screen since the activity might start from an
existing task, showing an icon on it might seems strange to user.

Bug: 183150443
Bug: 183108088
Test: atest StartingSurfaceDrawerTests ActivityRecordTests
Change-Id: Ia76648c291d602302725a1814991971a1d544549