test: change one iowatcher to a TODO

Problem: iowatcher test 5 'iowatcher returns error correctly'
tries to create an iowatcher watching a stream directory that
isn't a directory to elicit an ENOTDIR error.  This lookup is
now performed in a continuation, not directly in kz_set_ready_cb().
The kz_ready_f callback should be called, and when the user's
kz_get() is called, it will fail with ENOTDIR.

Mark this test a TODO for now.

t/lua/t1003-iowatcher.t

@@ -19,6 +19,7 @@ local iow, err = f:iowatcher {
     key = "simpleval",
     handler = function (iow, lines) end
 }
+todo ("error on dir lookup is now deferred kz_get from kz_ready_f callbackb", 1)
 is (iow, nil, "iowatcher returns error correctly")
 
 dir['iowatcher'] = nil