fix unittest break

Summary: It looks like the ubuntu version of gtest complains about this?

Test Plan:
Will watch jenkins fbthrift and proxygen builds

previous jenkins break:
https://ci-builds.fb.com/job/folly/2178/console

Reviewed By: bmatheny@fb.com

Subscribers: doug, folly-diffs@, yfeldblum, chalfant

FB internal diff: D2032761

Tasks: 6913742

Signature: t1:2032761:1430337624:ec65b26cf8da7d0d8c7e449f235de7147d4f17d6

Blame Revision: D2029802

folly/test/MapUtilTest.cpp

@@ -46,9 +46,9 @@ TEST(MapUtil, get_or_throw_specified) {
 TEST(MapUtil, get_optional) {
   std::map<int, int> m;
   m[1] = 2;
-  EXPECT_TRUE(get_optional(m, 1));
+  EXPECT_TRUE(get_optional(m, 1).hasValue());
   EXPECT_EQ(2, get_optional(m, 1).value());
-  EXPECT_FALSE(get_optional(m, 2));
+  EXPECT_FALSE(get_optional(m, 2).hasValue());
 }
 
 TEST(MapUtil, get_ref_default) {