etcd: make all service using etc go to 127.0.0.1:2379 by default

The old etcd port 4001 is no longer enabled by default in etcd 3.
The new port is 2379 and is officially assigned by IANA.

There were still some services left that expect etcd on port 4001 by default.
This changes the default to 2379 everywhere.

It should not cause problems for users as the etcd by nix does listen on the new port only by default anyway.