VintfObjectTest: fix properties

On devices with ro.boot.product.hardware.sku defined,
DeviceManifestTest actually fetches the value, causing
the test to fail. Set-up mocks correctly.

Test: run vintf_object_test on b1c1
Bug: 121205339
Change-Id: Ib34e9266a53cdd27337dd2da65926157a82cba55
diff --git a/test/vintf_object_tests.cpp b/test/vintf_object_tests.cpp
index 349426f..a0bfa78 100644
--- a/test/vintf_object_tests.cpp
+++ b/test/vintf_object_tests.cpp
@@ -774,6 +774,10 @@
 
 class DeviceManifestTest : public VintfObjectTestBase {
    protected:
+    virtual void SetUp() {
+        VintfObjectTestBase::SetUp();
+        setFakeProperties();
+    }
 
     // Expect that /vendor/etc/vintf/manifest.xml is fetched.
     void expectVendorManifest() { expectFetch(kVendorManifest, vendorEtcManifest); }