Narrow down the condition of wallpaper target for occluded keyguard

Previously, keyguard will be selected as the backup wallpaper target
if there keyguard is locked and there is an active transition. That
is to avoid wallpaper from being show/hide in a short time when
running recents transition to close app on keyguard.

The condition was a bit broad so the regular transition will also
keep wallpaper target on keyguard. Which could make the transition
change mode of wallpaper become CHANGE rather than TO_BACK when
launching an occlude-keyguard app and then display rotates. Which
could make the condition of seamless rotation rejects the seamless
effect because it found wallpaper is a changing operation.

To avoid such case, only enable the condition if there is a transient
(recents) transition.

Bug: 333557024
Test: Enable auto rotation. Set a secured lock. Turn off screen.
      Double click power key to launch camera when holding the
      device in landscape. There should not have a rotation animation.
Test: On a secured keyguard. Double click power key to launch camera.
      Swipe from bottom to dismiss camera. The wallpaper target
      should only change to notification shade once.
Test: atest WallpaperControllerTests#testShowWhenLockedWallpaperTarge

Change-Id: I43a29e828798f36f39d38af130f98de7c5859ec6