Download images as dependencies of roles

Pre download all required container images as roles' deps.
Drop unused flannel-server-helper images pre download.
Improve pods creation post-install test pre downloaded busybox.
Improve logs collection script with kubectl describe, fix sudo/etcd/weave
commands.

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

roles/network_plugin/flannel/meta/main.yml

@@ -1,6 +1,4 @@
 ---
 dependencies:
-  - role: download
-    file: "{{ downloads.flannel_server_helper }}"
   - role: download
     file: "{{ downloads.flannel }}"