Improve networks

Create a single external network called "external".
Create container-specific networks.
Only a few containers need access to these.
So far: openldap, postgres.

roles/openldap/tasks/main.yml

@@ -6,13 +6,19 @@
   loop:
     - "{{ data_folder }}/openldap"
     - "{{ data_folder }}/openldap/data"
+- name: create network
+  docker_network:
+    name: openldap
+    attachable: true
+    internal: true
+    state: present
 - name: run container
   docker_container:
     name: "openldap"
     image: osixia/openldap
     hostname: openldap
     networks:
-      - name: nginx-internal
+      - name: openldap
     ports:
       - "389:389"
       - "636:636"