fix valgrind errors

Uninitialized key caused the following error:

Conditional jump or move depends on uninitialised value(s)
   at ...: __memcmp_sse4_1 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   ...

tests/multi_test.c

@@ -3,7 +3,8 @@
 
 int multi_test(void)
 {
-   unsigned char key[32], buf[2][MAXBLOCKSIZE];
+   unsigned char key[32] = { 0 };
+   unsigned char buf[2][MAXBLOCKSIZE];
    unsigned long len, len2;
 
 /* register algos */