Constrain the generated key type in testing

[ Merge of http://go/wvgerrit/148157 ]

Fail the test if the returned type is other values.

Bug: 224375138
Test: GtsMediaDrmTests
Change-Id: I4abad9d69865cac99654d3dedd443463dd728a58

libwvdrmengine/oemcrypto/test/oemcrypto_test.cpp

@@ -1340,6 +1340,8 @@ TEST_F(OEMCryptoProv40Test, GenerateCertificateKeyPairSuccess) {
   } else if (key_type == OEMCrypto_PrivateKeyType::OEMCrypto_ECC_Private_Key) {
     ASSERT_NO_FATAL_FAILURE(
         s.SetEcPublicKey(public_key.data(), public_key_size));
+  } else {
+    FAIL() << "Unknown private key type: " << static_cast<int>(key_type);
   }
 }