Fix intermitent bad nonce being passed to RewrapDeviceRSAKey.

Since CryptoSession::RewrapDeviceRSAKey takes a const std::string& nonce, the calling code
implicitly constructa temporary std::string from a character array with undefined termination
and sometimes bogus value when nonce.data() is passed in.

Bug: 9016828

Merge of https://widevine-internal-review.googlesource.com/#/c/5690/
from the Widevine CDM repository

Change-Id: Ia3beaa5f1a96924a8cc53a719f25af52217b8cc5

libwvdrmengine/cdm/core/src/cdm_engine.cpp

@@ -725,7 +725,7 @@ CdmResponseType CdmEngine::HandleProvisioningResponse(
   std::string wrapped_rsa_key;
   if (!crypto_session->RewrapDeviceRSAKey(signed_message,
                                           signature,
-                                          nonce.data(),
+                                          nonce,
                                           enc_rsa_key,
                                           enc_rsa_key.size(),
                                           rsa_key_iv,