ACL: configure the master connection without user.

src/replication.c

@@ -1080,6 +1080,7 @@ void replicationCreateMasterClient(int fd, int dbid) {
     server.master->authenticated = 1;
     server.master->reploff = server.master_initial_offset;
     server.master->read_reploff = server.master->reploff;
+    server.master->user = NULL; /* This client can do everything. */
     memcpy(server.master->replid, server.master_replid,
         sizeof(server.master_replid));
     /* If master offset is set to -1, this master is old and is not