Ignore ui mode change caused by Morris overlay in PiP

When entering PiP from GMM with Morris overlay enabled, there will be a
display change callback caused by ui mode change that tend to shift the
PiP window. For PiP, such ui mode change from app is not quite relevant
and we can simply ignore in PipController.

Bug: 201589034
Video: http://recall/-/aaaaaabFQoRHlzixHdtY/dmI3KCeKPAH118BRqnhgNO
Test: enter PiP from GMM with Morris overlay, see video
Change-Id: I2d72e166fb8de1e503415b5441c03f0685de9573