Haven't error when use wrong port

By mistake I've used admin port (9991) instead of http (4181).
And run command: `namerctl dtab create incoming incoming --base-url "http://host:9991"`
After that I got message: **Created incoming** and didn't have an error

When I run: `namerctl dtab ls --base-url "http://host:9991"`
I got: `Error: invalid character '<' looking for beginning of value`

Start with the `namerctl dtab create` command and its `--base-url` handling, then compare its behavior with `namerctl dtab ls` when pointed at port 9991. Done means using the admin port does not report `Created incoming` silently and instead surfaces an appropriate error.

Written by the indexing model from the issue text.