Prevent waiting if no new activity instance launched

An existing task can be brought to front while starting
an Intent. In that case, the launching TaskFragment will
remain empty because no new activity instance created.

Monitor the activity launch result and prevent waiting
if the activity instance was not created and cleared the
pending appeared intent.

Bug: 233989810
Test: atest TaskFragmentContainerTest
Test: atest SplitControllerTest
Change-Id: I1bdf516673b71892921da14bdcdb9d1c23ce0a9a