libutils: Fix thread safety annotations in Mutex

The annotations for Mutex::tryLock and timedLock were
incorrectly specifying the return value for the successful
acquisition.

Test: make libutils_test
Change-Id: I9729b6555ede5cb1d6db046e33c35bf5926c7755
diff --git a/libutils/Mutex_test.cpp b/libutils/Mutex_test.cpp
index 8a1805f..79f4302 100644
--- a/libutils/Mutex_test.cpp
+++ b/libutils/Mutex_test.cpp
@@ -29,4 +29,20 @@
     android::Mutex::Autolock _l(mLock);
     i = 0;
     modifyLockedVariable();
-}
\ No newline at end of file
+}
+
+TEST(Mutex, tryLock) {
+    if (mLock.tryLock() != 0) {
+        return;
+    }
+    mLock.unlock();
+}
+
+#if defined(__ANDROID__)
+TEST(Mutex, timedLock) {
+    if (mLock.timedLock(1) != 0) {
+        return;
+    }
+    mLock.unlock();
+}
+#endif