Remove multiple logging implementations.

Change-Id: I7474c29b394f37918a35bba58b2fab58a7be930f
diff --git a/aos/testing/test_logging.cc b/aos/testing/test_logging.cc
index bc60081..1799cda 100644
--- a/aos/testing/test_logging.cc
+++ b/aos/testing/test_logging.cc
@@ -143,7 +143,7 @@
 
 void *DoEnableTestLogging() {
   logging::Init();
-  logging::AddImplementation(TestLogImplementation::GetInstance());
+  logging::SetImplementation(TestLogImplementation::GetInstance());
 
   ::testing::UnitTest::GetInstance()->listeners().Append(
       new MyTestEventListener());