Make sure CtsCheckpointTestCases passes

Bug: 141639903
Bug: 141499347
Test: Cts test CtsCheckpointTestCases passes
Change-Id: Id5e9c0df969340e0b8f08436daa027614c45b380
diff --git a/Checkpoint.cpp b/Checkpoint.cpp
index a4e8fc8..b2b648f 100644
--- a/Checkpoint.cpp
+++ b/Checkpoint.cpp
@@ -344,6 +344,8 @@
 }  // namespace
 
 Status cp_prepareCheckpoint() {
+    // Log to notify CTS - see b/137924328 for context
+    LOG(INFO) << "cp_prepareCheckpoint called";
     std::lock_guard<std::mutex> lock(isCheckpointingLock);
     if (!isCheckpointing) {
         return Status::ok();