Failed to set dashboard-address if TLS certificate is configured and client-urls scheme is set to http

## Bug Report

### What did you do?

* Start a cluster with TLS configured, but set the `client-urls` scheme to `http`
* `pd-ctl -u "http://{PD_ADDRESS}" config set "dashboard-address" "{PD_ADDRESS}"`
> PD_ADDRESS only has IP and port, no scheme

### What did you expect to see?

* The `dashboard-address` config is updated successfully.

### What did you see instead?

* The `dashboard-address` config is updated failed.

### What version of PD are you using (`pd-server -V`)?

#2517

### Note

When the `dashboard-address` is set without specifying a scheme, it will be supplemented according to whether or not a TLS certificate is configured, which may not match the address in the `client-urls`.

Maybe we should restrict the scheme of `client-urls` and `peer-urls` to be `https` when the TLS certificate is set.