[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
diff --git a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
index ca1b6d8..d3a5dc8 100644
--- a/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
+++ b/graphics/composer/aidl/vts/VtsHalGraphicsComposer3_TargetTest.cpp
@@ -1773,6 +1773,7 @@
 }
 
 TEST_P(GraphicsComposerAidlCommandTest, SetDisplayBrightness) {
+    EXPECT_TRUE(mComposerClient->setPowerMode(getPrimaryDisplayId(), PowerMode::ON).isOk());
     const auto& [status, capabilities] =
             mComposerClient->getDisplayCapabilities(getPrimaryDisplayId());
     ASSERT_TRUE(status.isOk());