Fix notifyTaskDisplayChanged is called every time onDisplayChanged is triggered.

The original intention was to send the callback
when the task reparented to another display.
So we need to add a check whether displayId has
changed before calling notifyTaskDisplayChanged.

Test: pressure test that notifyTaskDisplayChanged
is triggered when the task moves from one display
to another, and not triggered otherwise.
Bug: b/365477008

Change-Id: I5848ead17a50ccd6ece0e3b0c10e59252a633f89
Signed-off-by: zhou.wei <zhou.wei@oppo.com>