Update OpenStack Terraform: Modules, Bastions, and New Floating IP config (#1958)

* Adding bastion and private network provisioning for openstack terraform

* Remove usage of floating-ip property

* Combine openstack instances + floating ips

* Fix relating floating IPs to hosts for openstack builds

* Tighten up security groups

Allow ssh into all instances with floating IP

* Add the gluster hosts to the no-floating group

* Break terraform into modules

* Update README and var descriptions to match current config

* Remove volume property in gluster compute def

* Include cluster name in internal network and router names

* Make dns_nameservers a variable