Add Property for Provisioning ID

Adds a property that allows applications to get the provisioning-unique serial
number.

Bug: 9175567

Also fixes some missing mutexes that were causing intermittent failures in
calls to OEMCrypto due to concurrency issues.

Bug: 9175583

Merge of https://widevine-internal-review.googlesource.com/#/c/5831/
from the Widevine CDM repository

Change-Id: I1d7e3ca9f3b06da345022f5f0d64e0c17a5cedca

libwvdrmengine/cdm/test/request_license_test.cpp

@@ -534,6 +534,10 @@ TEST_F(WvCdmRequestLicenseTest, QueryStatus) {
   EXPECT_TRUE(ss >> system_id);
   EXPECT_TRUE(ss.eof());
 
+  itr = query_info.find(wvcdm::QUERY_KEY_PROVISIONING_ID);
+  ASSERT_TRUE(itr != query_info.end());
+  EXPECT_EQ(16, (int)itr->second.size());
+
   decryptor_.CloseSession(session_id_);
 }