Sync fake clock for nonce tests

Because the fake clock is getting out of sync with the real clock
for the nonce flood tests, add a call to TestSleep::SyncFakeClock()
in Clock::GetCurrentTime() to force a sync.

Merged from http://go/wvgerrit/133223

Test: duration_use_case_test and nonce flood tests on bonito
Bug: 198329759
Change-Id: Idfd92c6cc57750a52477189461220c682b302082

libwvdrmengine/cdm/util/test/test_clock.cpp

@@ -35,6 +35,7 @@ FakeClock* g_fake_clock = nullptr;
 
 // On devices running a fake OEMCrypto, we can use a fake sleep and fake time.
 int64_t Clock::GetCurrentTime() {
+  wvcdm::TestSleep::SyncFakeClock();
   if (g_fake_clock == nullptr) g_fake_clock = new FakeClock();
   return g_fake_clock->now() / 1000;
 }