Fix a buffer overflow in setup_cfg() in src/test/test_voting_flags.c

signed_descriptor_digest has a length of DIGEST_LEN but the memset
used to fill it used DIGEST256_LEN.

Signed-off-by: Kris Katterjohn <katterjohn@gmail.com>

src/test/test_voting_flags.c

@@ -35,7 +35,7 @@ setup_cfg(flag_vote_test_cfg_t *c)
   strlcpy(c->expected.nickname, "testing100", sizeof(c->expected.nickname));
 
   memset(c->ri.cache_info.identity_digest, 0xff, DIGEST_LEN);
-  memset(c->ri.cache_info.signed_descriptor_digest, 0xee, DIGEST256_LEN);
+  memset(c->ri.cache_info.signed_descriptor_digest, 0xee, DIGEST_LEN);
 
   c->ri.cache_info.published_on = c->now - 100;
   c->expected.published_on = c->now - 100;