Fix tests on resolving freeform launch

Only return RESULT_DONE if params have resolved to freeform windowing
mode.

Flag: com.android.window.flags.enable_freeform_display_launch_params
Bug: 401564801
Test: atest DesktopModeLaunchParamsModifierTests
      atest WindowMetricsActivityTests
      atest FreeformWindowingModeTests
Change-Id: I3d7e5d8d861f9d1dc291c4a81c4521101e9e9d75