Test CannotCreateEarlyBootKeys only if metadata encryption is on

In R, earlyBootEnded is called only when metadata encryption is being
set up, and thus is not called if metadata encryption is not enabled.
So don't test it under those circumstances.

Bug: 170875742
Test: Cherry-pick aosp/1515419 so that this test can fail. Test passes
    with metadata encryption enabled or disabled, but does not pass
    if metadata encryption is enabled and earlyBootEnded is
    commented out. (Cuttlefish)
Change-Id: I4f1704ca6235d47a1b47902ebbcc1720d016e8dd

keymaster/4.1/vts/functional/EarlyBootKeyTest.cpp

@@ -18,6 +18,8 @@
 
 #include <keymasterV4_1/authorization_set.h>
 
+#include <android-base/properties.h>
+
 namespace android::hardware::keymaster::V4_1::test {
 
 using std::string;
@@ -30,6 +32,8 @@ using EarlyBootKeyTest = Keymaster4_1HidlTest;
 // creates/uses early boot keys during boot.  It should fail to boot if the early boot key usage
 // fails.
 TEST_P(EarlyBootKeyTest, CannotCreateEarlyBootKeys) {
+    // In R, this works only on devices with metadata encryption.
+    if (!android::base::GetBoolProperty("ro.crypto.metadata.enabled", false)) return;
     auto [aesKeyData, hmacKeyData, rsaKeyData, ecdsaKeyData] =
             CreateTestKeys(TAG_EARLY_BOOT_ONLY, ErrorCode::EARLY_BOOT_ENDED);