exit: support custom VRF imports

Ten minutes to set up and ten hours to convince Ansible to not be
quite so retarded. The list2dict filter seems to be the (or another)
missing piece. Now let’s rewrite everything else using it. Or not.

roles/exit/tasks/dhcp.yml

@@ -5,7 +5,7 @@
 - name: Install keepalived
   import_tasks: keepalived.yml
 
-- name: Configure relay for old DHCP server
+- name: Configure DHCP relays
   template:
     dest: '/etc/default/isc-dhcp-relay-{{ prefixes | selectattr("prefix", "==", item.0 | ipaddr("network/prefix")) | map(attribute="vrf.name") | first }}'
     src: isc-dhcp-relay.j2