Fix ambiguous reference to WARNING when using miniglog.

- When compiling on Clang on OS X with MINIGLOG enabled, name lookup
  finds two ambiguous definitions of WARNING, one in the global
  namespace and one in the google namespace, both defined in the
  miniglog version of logging.h.

Change-Id: I6f1ad7d2750e1ed20ec1ba4574aab599086431df
diff --git a/internal/ceres/levenberg_marquardt_strategy_test.cc b/internal/ceres/levenberg_marquardt_strategy_test.cc
index 86054fd..45e4da4 100644
--- a/internal/ceres/levenberg_marquardt_strategy_test.cc
+++ b/internal/ceres/levenberg_marquardt_strategy_test.cc
@@ -155,7 +155,7 @@
     EXPECT_CALL(log, Log(GLOG_WARNING, _,
                          HasSubstr("Failed to compute a step")));
 #else
-    EXPECT_CALL(log, Log(WARNING, _,
+    EXPECT_CALL(log, Log(google::WARNING, _,
                          HasSubstr("Failed to compute a step")));
 #endif