OEMCrypto Unit Test Fix: Do Not Derive Keys Immediately

(This is a merge of http://go/wvgerrit/100053.)

The OEMCrypto Unit Tests were previously deriving keys from the session
key as part of loading the test RSA key. This creates an invalid
function call order, since the OEMCrypto session will likely next be
used for actions that need to be done *before* deriving these keys. With
ODKiTEE, which is more strict about this order, all OEMCrypto tests were
failing.

Bug: 156655072
Test: OEMCrypto Unit Tests
Change-Id: Ibfede587da30cfff4a44a5e0687e4199b1430372

libwvdrmengine/oemcrypto/test/oemcrypto_session_tests_helper.cpp

@@ -81,6 +81,6 @@ void SessionUtil::InstallTestRSAKey(Session* s) {
     ASSERT_NO_FATAL_FAILURE(s->InstallRSASessionTestKey(wrapped_rsa_key_));
   }
   // Test RSA key should be loaded.
-  ASSERT_NO_FATAL_FAILURE(s->GenerateDerivedKeysFromSessionKey());
+  ASSERT_NO_FATAL_FAILURE(s->PreparePublicKey());
 }
 }  // namespace wvoec