Parameterize apt repo endpoints

This allows overriding of apt repo endpoints when internet sources are not accessible. Additionally, switch to using the dockerproject.org gpg key url for apt instead of keyservers.net

roles/docker/tasks/main.yml

@@ -34,7 +34,7 @@
   action: "{{ docker_repo_key_info.pkg_key }}"
   args:
     id: "{{item}}"
-    keyserver: "{{docker_repo_key_info.keyserver}}"
+    url: "{{docker_repo_key_info.url}}"
     state: present
   register: keyserver_task_result
   until: keyserver_task_result|succeeded