Reserve enough user request stack space in pthread_create.

Bug: 18830897
Change-Id: I1ba4aaeaf66a7ff99c5d82ad45469011171b0a3b
diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 4fc5bed..1418c76 100644
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -644,8 +644,7 @@
   ASSERT_EQ(0, pthread_attr_getstacksize(&attributes, &stack_size));
   ASSERT_EQ(32*1024U + 1, stack_size);
 #if defined(__BIONIC__)
-  // Bionic rounds up, which is what POSIX allows.
-  ASSERT_EQ(GetActualStackSize(attributes), (32 + 4)*1024U);
+  ASSERT_EQ(GetActualStackSize(attributes), 32*1024U + 1);
 #else // __BIONIC__
   // glibc rounds down, in violation of POSIX. They document this in their BUGS section.
   ASSERT_EQ(GetActualStackSize(attributes), 32*1024U);