Only request power state of default display

Only the default display can have its power state controlled at this
time. Avoid requesting power state of any other display to avoid
initializing DisplayPowerController which does not shut itself down
properly in the event that a display is removed.

Bug: 178153032
Test: atest android.server.wm.DisplayCutoutTests#testDisplayCutout_never
Change-Id: Iea75815802d2759cba4f93d020c6c3700fee82a6