Openstack cloud network, security group, floating IP filtering based on selected tenant

https://bugzilla.redhat.com/show_bug.cgi?id=1142487

Filter configuration items based on selected tenant, if the tenant is not selected it uses the provider to list all the configuration items.
@blomquisg Can you confirm how the tenant field should work in the UI which will help drive what settings we need here?

Should this be a required field?  Is there a use case for NOT specifying a tenant?

With a single tenant connect to the provider:
1. Tenant selected by default and cannot be changed.
2. Tenant selected by default but can be set to None.
3. Tenant defaults to None and the user can select the tenant if desired.

Two or more tenants: Cloud tenant defaults to None and the user can select one.