Download containers and save all

Move version/repo vars to download role.
Add container to download params, which overrides url/source_url,
if enabled.
Fix networking plugins download depending on kube_network_plugin.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/kubernetes/master/meta/main.yml

@@ -1,4 +1,4 @@
 ---
 dependencies:
-  - role: download # For kube_version variable
-    file: "{{ downloads.nothing }}"
+  - role: download
+    file: "{{ downloads.hyperkube }}"