rax provisioning refactored in w/ openstack provisioning

* added support for provisioning rackspace nodes to khaleesi
* refactored the directory layout of get_nodes and cleanup to
  support multiple provioning env
* set the default provisioning env to "openstack" in functions.sh
* tested provisioning and cleanup w/ both rackspace and openstack
* default added to sites/default.yml
* settings.py updated

wip: add rax provisioning

Change-Id: I7c169dec21653578fa6c1da0b0b39b426768ec12

provisioning working

Change-Id: Ie12e0f1b3727d49284fc7c9ddc1c9e470dca2a06

rax provisioning refactored in w/ openstack provisioning

Change-Id: I2d3561ea02e732f8e3c55ff3c6ac70f9759e6ed8