Relax the result-to restriction if activity is finishing

Because the finishing activity won't get the results anyway.

Though, the caller activity was using start-for-result to
start a singleTask activity of another app on the
caller's task.

Bug: 236668365
Bug: 241071379
Test: atest TaskFragmentTest
Change-Id: I94e1f0aab35ceec341dc9acb3b9f749ef9c0cf21