[VTS] Update SetDisplayBrightness test item

Ensure the primary display power on before run the
SetDisplayBrightness test item.

Bug: 313794734
Test: atest VtsHalGraphicsComposer3_TargetTest:PerInstance/
      GraphicsComposerAidlCommandTest#SetDisplayBrightness/
      0_android_hardware_graphics_composer3_IComposer_default
      -- --abi arm64-v8a
Change-Id: I94fb700704bcbd8543f2a608dd75b9e745e40e37
Merged-In: I94fb700704bcbd8543f2a608dd75b9e745e40e37