leak_detective: Assign return value of realloc to buf

If realloc return a pointer value different from the value to be
reallocated, a double free can occur in this context.

Signed-off-by: Thomas Egerer <thomas.egerer@secunet.com>

src/libstrongswan/utils/leak_detective.c

@@ -483,7 +483,7 @@ static void* real_realloc(void *ptr, size_t size)
 static bool register_hooks()
 {
 	void *buf = real_malloc(8);
-	real_realloc(buf, 16);
+	buf = real_realloc(buf, 16);
 	real_free(buf);
 	return TRUE;
 }