Only set task surface corner radius once in TransformParams

When setting the corner radius constantly in TransformParams sometimes
we set the radius after the end of the recents transition, causing
Desktop tasks to have non-rounded corners at the end of recents
transitions.

Bug: 378657004
Test: manual + TransformParamsTest
Flag: com.android.window.flags.enable_desktop_recents_transitions_corners_bugfix
Change-Id: I2ae919424602d655d0995b4dc1951d96c7dfd3d8