Tweak IMapper 4.0 VTS to run with AIDL IAllocator

When there is no HIDL IAllocator installed on the device, then these
tests must still run.

Bug: 231982605
Test: VtsHalGraphicsMapperV4_0TargetTest
Change-Id: If7503d398c03086df470971cc2c10029270525f9
diff --git a/graphics/composer/2.1/utils/vts/ComposerVts.cpp b/graphics/composer/2.1/utils/vts/ComposerVts.cpp
index 55aaf12..e777010 100644
--- a/graphics/composer/2.1/utils/vts/ComposerVts.cpp
+++ b/graphics/composer/2.1/utils/vts/ComposerVts.cpp
@@ -318,7 +318,7 @@
     [this] {
         ASSERT_NO_FATAL_FAILURE(mGralloc4 = std::make_shared<Gralloc4>("default", "default",
                                                                        /*errOnFailure=*/false));
-        if (mGralloc4->getAllocator() == nullptr || mGralloc4->getMapper() == nullptr) {
+        if (!mGralloc4->hasAllocator() || mGralloc4->getMapper() == nullptr) {
             mGralloc4 = nullptr;
             ASSERT_NO_FATAL_FAILURE(mGralloc3 = std::make_shared<Gralloc3>("default", "default",
                                                                            /*errOnFailure=*/false));