Do not resolve activity creation if it is in unknown TaskFragment

This can happen in two cases:
1. The activity is embedded in another app. Then the current organizer
   shouldn't control it.
2. The activity is in a TaskFragment that the organizer just request to
   remove, but hasn't reach the server side. Then the activity will soon
   be finished with the TaskFragment.

In either case, the organizer shouldn't need to resolve it. Otherwise it
may incorrectly change the state, such as entering split for a finishing
activity.

Bug: 233295443
Test: atest WMJetpackUnitTests:SplitControllerTest
Change-Id: I5d2028dd45abd8d20a8e82bc4e51c4d6dc6e26ee