Use AUTH_TYPE_NONE consistently.

configuration.c

@@ -783,7 +783,6 @@ parse_key(int c, gnc_t gnc, void *closure, struct key **key_return)
             } else if(strcmp(auth_type, "blake2s") == 0) {
                 key->type = AUTH_TYPE_BLAKE2S;
             } else {
-                key->type = 0;
                 free(auth_type);
                 goto error;
             }

hmac.c

@@ -72,7 +72,7 @@ add_key(char *id, int type, int len, unsigned char *value)
 {
     struct key *key;
 
-    assert(value != NULL && type != 0);
+    assert(value != NULL && type != AUTH_TYPE_NONE);
 
     key = find_key(id);
     if(key) {

message.c

@@ -1074,12 +1074,12 @@ flushbuf(struct buffered *buf, struct interface *ifp)
     assert(buf->len <= buf->size);
 
     if(buf->len > 0) {
-        if(ifp->key != NULL && ifp->key->type != 0)
+        if(ifp->key != NULL && ifp->key->type != AUTH_TYPE_NONE)
             send_crypto_seqno(buf, ifp);
         debugf("  (flushing %d buffered bytes)\n", buf->len);
         DO_HTONS(packet_header + 2, buf->len);
         fill_rtt_message(buf, ifp);
-        if(ifp->key != NULL && ifp->key->type != 0) {
+        if(ifp->key != NULL && ifp->key->type != AUTH_TYPE_NONE) {
             end = add_hmac(buf, ifp, packet_header);
             if(end < 0) {
                 fprintf(stderr, "Couldn't add HMAC.\n");