nixos/jenkins: rename option 'host' to 'listenAddress'

I think the name 'listenAddress' is more descriptive. Other NixOS
modules that define 'host' either use it as listen address or as address
a client connects to. listenAddress is unambiguous.

The addition of 'host' was added earlier today[1], so not bothering with
./nixos/modules/rename.nix.

[1]: 44ea1849 ("jenkins ci enhancement: add port and prefix option")