Rerun network setup on deployed nodes

[OpenStack Infra]

https://review.openstack.org/250507
commit d53c75bf3a0b9da2e36d5a9914ecd5a3997524f5
Author: Aleksey Kasatkin <email address hidden>
Date: Thu Nov 26 19:45:53 2015 +0200

    Rerun network setup on deployed nodes

    This is required to apply changes that could be made to the networking
    configuration of environment.
    The major case is: add/remove node network group(s).

    The configuration changes are not tracked as nailgun does not have
    proper functionality for that.

    New key is introduced in task description: reexecute_on (list).
    Deployment tasks which are to be re-executed on deploy changes must have

    reexecute_on:
      - deploy_changes

    DocImpact

    Change-Id: I668fcb426826cecf69a5c7fc1e92b8ae8dfeef9f
    Blueprint: redeploy-network-on-changes