Separate out the Cloud Files tenant_id and regular Cloud tenant_id

Cloud Files uses the MossoFS tenant, this is not the same as the
tenant_id used for authenticating with Rackspace Cloud.

* Separate out the 2 settings in user_variables to ensure these are
  noted as being different values.

Fixes #103
Merge pull request #111 from andymcc/cloudfiles_tenant_fix

Separate out the Cloud Files tenant_id and regular Cloud tenant_id