Make sure an isolated removeTask becomes ready

If this removeTask happens without any consequent actions
(eg. removing a pip task and nothing starts as a result), the
transition system needs to interpret it as ready immediately.

Bug: 339135761
Test: Open netflix video in pip, go to recents and restore netflix
Change-Id: I14bed6164e12bd4d36c24870738188f5e89a4eb1
Merged-In: I14bed6164e12bd4d36c24870738188f5e89a4eb1
(cherry picked from commit 31a9c1f4ff2310f51625b9b5e975a5f501316a0b)