CORD-536 updated to support the setting of repo via vars

Change-Id: I84988b634967d8be2e5a9f3a79352be5efa9c0c0
diff --git a/roles/docker/meta/main.yml b/roles/docker/meta/main.yml
index bf39d8c..ca35ded 100644
--- a/roles/docker/meta/main.yml
+++ b/roles/docker/meta/main.yml
@@ -12,4 +12,5 @@
   galaxy_tags:
     - development
     - system
-dependencies: []
+dependencies:
+  - { role: local-ubuntu-repository, when: ubuntu_apt_repo is defined }