call uselocale() before freelocale() to make sure that g_local_key has a valid locale.

For tests that call uselocale(), the locale is stored in the
g_userlocale_key thread-specific key. If freelocale() is called later,
then g_uselocal_key points to a deleted pointer. CTS eventually calls
vfprintf to print the result, which calls MB_CUR_MAX and MB_CUR_MAX
accesses the deleted locale stored in g_uselocale_key, causing unpredictable
errors.

Fixed the tests by calling uselocale() with the old locale before
calling freelocale.

(cherry-pick of 8a46cf0fcf82b8c76e05be7e066ec854f974603a.)

Bug: 17299565
Change-Id: I87efa2a9b16999a11d587f68d3aeedcbe6ac8a2c
diff --git a/tests/locale_test.cpp b/tests/locale_test.cpp
index 325f6ce..7ec607a 100644
--- a/tests/locale_test.cpp
+++ b/tests/locale_test.cpp
@@ -114,11 +114,12 @@
   locale_t cloc = newlocale(LC_ALL, "C", 0);
   locale_t cloc_utf8 = newlocale(LC_ALL, "C.UTF-8", 0);
 
-  uselocale(cloc);
+  locale_t old_locale = uselocale(cloc);
   ASSERT_EQ(1U, MB_CUR_MAX);
   uselocale(cloc_utf8);
   ASSERT_EQ(4U, MB_CUR_MAX);
 
+  uselocale(old_locale);
   freelocale(cloc);
   freelocale(cloc_utf8);
 }