Replace hardcoded node svc address in admin crate with configured node svc address

[tillrohrmann]

In order to support differently configured node svc addresses, the admin crate must not assume that it is running on 127.0.0.1:5122. Instead it should read it from the configuration. https://github.com/restatedev/restate/blob/e3bfec752620f37cfb387d6229a924462b059158/crates/node/src/roles/admin.rs#L114.