Document and update fileserver roles

The add-fileserver role needs to be used by a job in a config repo as it
performs local actions such as adding a host to the inventory and needs to
be run on localhost.

publish-artifacts-to-fileserver doesn't have any special requirements, but
it's fairly useless without the first role.

Change-Id: I0e37ee297b13dceb70300a4f8f4accc233254df3

roles/add-fileserver/tasks/main.yaml

@@ -1,21 +1,22 @@
 - name: Create SSH private key from secret
   copy:
     content: "{{ fileserver.ssh_private_key }}"
-    dest: ~/.ssh/tarballs_id_rsa
+    dest: ~/.ssh/fileserver_id_rsa
     mode: 0600
 
-- name: Add tarballs server ssh key
-  command: ssh-add ~/.ssh/tarballs_id_rsa
+- name: Add fileserver ssh key
+  command: ssh-add ~/.ssh/fileserver_id_rsa
 
 - name: Remove SSH private key from disk
-  command: shred ~/.ssh/tarballs_id_rsa
+  command: shred ~/.ssh/fileserver_id_rsa
 
-- name: Add tarballs server to inventory
+- name: Add fileserver to inventory
   add_host:
     name: "{{ fileserver.fqdn }}"
-    ansible_user: "{{ fileserver.ssh_username }}"
+    ansible_user: "{{ fileserver.ssh_username|default(ansible_user) }}"
+    zuul_fileserver_project_path: "{{ fileserver.path }}/{{ zuul.project.short_name }}"
 
-- name: Add tarballs server to known hosts
+- name: Add fileserver server to known hosts
   known_hosts:
     name: "{{ fileserver.fqdn }}"
     key: "{{ fileserver.ssh_known_hosts }}"