Change from Nova security groups to Neutron (#2910)

* Replace `openstack_compute_secgroup_v2` with `openstack_networking_secgroup_v2`

The `openstack_networking_secgroup_v2` resource allow specifications of
both ingress and egress. Nova security groups define ingress rules only.

This change will also allow for more user-friendly specified security
rules, as the different security group resources have different HCL
syntax.