devstack: support for multinode scenarios
devstack: support for multinode scenarios

Updates devstack plugin to execute tasks according to node role.

Signed-off-by: Francesco Santoro <francesco.santoro@6wind.com>

Change-Id: Id1ca39f27a9c3989fefd78b90a238ae18bb2a737

openstack/networking-6wind,stackforge/networking-6wind,openstack/networking-6wind,stackforge/networking-6wind