Fix transition wait when ActivityEmbedding enters PiP

Make sure we don't wait for unnecessary case when entering PiP from
ActivityEmbedding.

Bug: 225371112
Test: manually verify with Video app.
Test: atest WmTests:TaskFragmentTest
Change-Id: I6e8d60be49ddb947e7788b3ef7b58cc492888004
5 files changed