Fix AZP tests, add current_container_facts module (#48)

* Add new facts module for determining whether the module is running inside a container or not.

* Add containers to main network.

* Fix running tests locally with newer docker.

* Simplify setup_openssl to only install cryptography.

* Add alias in network.

* Make sure to upgrade cryptography to something more sensible on Ubuntu 16.04.

* Don't jump through hoops for bridge.

* Try to use other IPv4 nets.

* Improve module docs.

tests/integration/targets/setup_docker_registry/tasks/setup-frontend.yml

@@ -11,10 +11,18 @@
     name: '{{ docker_registry_container_name_frontend }}'
     image: "{{ docker_test_image_registry_nginx }}"
     ports: 5000
+    # `links` does not work when using a network. That's why the docker_container task
+    # in setup.yml specifies `aliases` so we get the same effect.
     links:
     - '{{ docker_registry_container_name_registry }}:real-registry'
     volumes:
     - '{{ docker_registry_container_name_frontend }}:/etc/nginx/'
+    network_mode: '{{ current_container_network_ip | default(omit, true) }}'
+    networks: >-
+      {{
+        [dict([['name', current_container_network_ip]])]
+        if current_container_network_ip not in ['', 'bridge'] else omit
+      }}
   register: nginx_container
 
 - name: Copy static files into volume
@@ -65,9 +73,17 @@
     debug:
       var: nginx_container.container.NetworkSettings
 
+  - name: Get registry URL
+    set_fact:
+      # Note that this host/port combination is used by the Docker daemon, that's why `localhost` is appropriate!
+      # This host/port combination cannot be used if the tests are running inside a docker container.
+      docker_registry_frontend_address: localhost:{{ nginx_container.container.NetworkSettings.Ports['5000/tcp'].0.HostPort }}
+      # The following host/port combination can be used from inside the docker container.
+      docker_registry_frontend_address_internal: "{{ nginx_container.container.NetworkSettings.Networks[current_container_network_ip].IPAddress if current_container_network_ip else nginx_container.container.NetworkSettings.IPAddress }}:5000"
+
   - name: Wait for registry frontend
     uri:
-      url: https://{{ nginx_container.container.NetworkSettings.IPAddress }}:5000/v2/
+      url: https://{{ docker_registry_frontend_address_internal }}/v2/
       url_username: testuser
       url_password: hunter2
       validate_certs: false
@@ -76,10 +92,6 @@
     retries: 5
     delay: 1
 
-  - name: Get registry URL
-    set_fact:
-      docker_registry_frontend_address: localhost:{{ nginx_container.container.NetworkSettings.Ports['5000/tcp'].0.HostPort }}
-
 - set_fact:
     docker_registry_frontend_address: 'n/a'
   when: can_copy_files is failed