Unit test for loading nonce-free offline license

Merge from Widevine repo of http://go/wvgerrit/100964

The previous nonce-free test used the same session to generate the
request as to load the license. However, it is a realistic use case to
have a new session used for loading the license.

The use case relates to a pre-loaded, shared license.

Test: Ran unit tests on taimen and on v16 ref implementation
Bug: 156853321
Change-Id: Ibc07744a16edcd3952d88d73660a75d0c3e8eeb8

libwvdrmengine/oemcrypto/test/oec_session_util.h

@@ -298,7 +298,7 @@ class LicenseRoundTrip
   // Reload an offline license into a different session. This derives new mac
   // keys and then calls LoadResponse.
   OEMCryptoResult ReloadResponse(Session* session);
-  void VerifyTestKeys();
+  void VerifyTestKeys(Session* session);
   // Set the default key control block for all keys. This is used in
   // CreateDefaultResponse.  The key control block determines the restrictions
   // that OEMCrypto should place on a key's use. For example, it specifies the