test/reduce: construct fake tbon attrs

Add fake attributes for tbon.level and tbon.maxlevel so
flux_reduce_create() can succeed in FLUX_REDUCE_TIMEDFLUSH
mode when the handle is was opened on the loop connector.

t/loop/reduce.c

@@ -264,6 +264,8 @@ void test_timed (flux_t h)
  ok ((r = flux_reduce_create (h, reduce_ops, 0.1, NULL,
  FLUX_REDUCE_TIMEDFLUSH)) != NULL,
  "timed: flux_reduce_create works");
+ if (!r)
+ BAIL_OUT();
  ok (flux_reduce_opt_get (r, FLUX_REDUCE_OPT_TIMEOUT, &timeout,
  sizeof (timeout)) == 0 && timeout == 0.1,
  "timed: timeout scaled by 1.0 on rank 0");
@@ -351,6 +353,10 @@ int main (int argc, char *argv[])
  if (!h)
  BAIL_OUT ("can't continue without loop handle");
 
+ flux_attr_fake (h, "rank", "0", FLUX_ATTRFLAG_IMMUTABLE);
+ flux_attr_fake (h, "tbon.level", "0", FLUX_ATTRFLAG_IMMUTABLE);
+ flux_attr_fake (h, "tbon.maxlevel", "0", FLUX_ATTRFLAG_IMMUTABLE);
+
  test_nopolicy (h); // 6
  test_hwm (h); // 37
  test_timed(h); // 18