roles/koji-client: Configure the koji client

The *koji-client* role is a generic role that can be used to configure
the Koji client library/`koji` CLI tool. By default, it manages the
default configuration at `/etc/koji`, but by using the
`koji_client_dir`, `koji_client_user`, and `koji_client_id` variables,
it can be used to configure per-user client configuration as well.

roles/koji-client/templates/config.j2

@@ -0,0 +1,11 @@
+[koji]
+server = {{ kojihub_url }}
+weburl = {{ kojiweb_url }}
+topurl = {{ kojifiles_url }}
+
+authtype = ssl
+cert = ~/.koji/client.pem
+ca = ~/.koji/clientca.crt
+serverca = ~/.koji/serverca.crt
+
+anon_retry = yes