broker/log.c: drop redundant rank setting

Problem: logbuf_initialize() calls flux_attr_set_cacheonly()
on the "rank" attribute.  The call to create_dummyattrs()
right after logbuf_initialize() handles this and there is
no reason to have it set early.

Drop this call.

src/broker/log.c

@@ -668,13 +668,6 @@ static void logbuf_finalize (void *arg)
     /* FIXME: need logbuf_unregister_attrs() */
 }
 
-static int fake_rank (flux_t *h, uint32_t rank)
-{
-    char buf[16];
-    snprintf (buf, sizeof (buf), "%u", rank);
-    return flux_attr_set_cacheonly (h, "rank", buf);
-}
-
 int logbuf_initialize (flux_t *h, uint32_t rank, attr_t *attrs)
 {
     logbuf_t *logbuf = logbuf_create ();
@@ -684,8 +677,6 @@ int logbuf_initialize (flux_t *h, uint32_t rank, attr_t *attrs)
     logbuf->rank = rank;
     if (logbuf_register_attrs (logbuf, attrs) < 0)
         goto error;
-    if (fake_rank (h, rank) < 0)
-        goto error;
     if (flux_msg_handler_addvec (h, htab, logbuf, &logbuf->handlers) < 0)
         goto error;
     flux_log_set_appname (h, "broker");