Initialize "buf" to 0 to make valgrind happy :-)

Note: the RAND_bytes() manual page says:
 RAND_bytes() puts num cryptographically strong pseudo-random bytes into buf.
It does not talk about using the previous contents of buf so we are working
as documented.

crypto/rand/rand_lib.c

@@ -154,6 +154,7 @@ void RAND_add(const void *buf, int num, double entropy)
 int RAND_bytes(unsigned char *buf, int num)
 	{
 	const RAND_METHOD *meth = RAND_get_rand_method();
+	memset(buf, 0, num);
 	if (meth && meth->bytes)
 		return meth->bytes(buf,num);
 	return(-1);
@@ -162,6 +163,7 @@ int RAND_bytes(unsigned char *buf, int num)
 int RAND_pseudo_bytes(unsigned char *buf, int num)
 	{
 	const RAND_METHOD *meth = RAND_get_rand_method();
+	memset(buf, 0, num);
 	if (meth && meth->pseudorand)
 		return meth->pseudorand(buf,num);
 	return(-1);