Skip sending TaskInfo change while not in pip

When recents animation finishes, it eventually triggers
ActivityRecord.setPictureInPictureParams if the Activity is pip-able.
And in the autoEnterPip case, this happens before the windowing mode
being flipped to PINNED and therefore callbacks the
FullscreenTaskListener and resets the leash to (0, 0).

Since it does not make sense dispatching TaskInfo change
while not in pinned mode, we simply skip it here.

Video: http://rcll/aaaaaabFQoRHlzixHdtY/eFlluOg7dAqjzsS6G8UYoX
Bug: 177073398
Test: see video
Change-Id: I782f94a1b5fe19973f21e1694b8d688575f1b7e8