[PIP2] Fix rounded corners for lock/unlock case

Fixes the lack of rounded corner and shadow radii when locking and
unlocking the device

Bug: 385152045
Flag: com.android.wm.shell.enable_pip2
Test: http://recall/-/cidfAmGe9UaIuFMHR3GEC8/bhYJXbiTEpxibFV5XG4Mmy
Change-Id: Ia247b9a81aee58b8689504724895c1d5ba0ce1e9