Add api calls to os in assert_cluster_ready

We should to stop use exec os command over ssh
and start to use python clients for cluster
verification.
This patch includes:
* add some api calls to the helpers.os_action
* checkers.image_list start to use api calls
* checkers.service_list move from nova-message
  usage to nova.services.list()
* checkers.netwotk_list start to use nova.networks.list()
* Test were updated

Change-Id: I2f042b3c8215611ce2c1a6f0cf37ccd03bbdf967
Closes-Bug: #1385420
Merge "Add api calls to os in assert_cluster_ready"