Swift auth does not work with Rackspace APIs

[Jamie Hannaford]

Currently most of the tests use the standard KeyStone Tenant Id to authenticate with Swift:

https://github.com/stackforge/openstack-sdk-php/blob/master/test/TestCase.php#L132

The problem, however, is that Rackspace's implement of Swift (Cloud Files) does not use the standard KeyStone Tenant Id. Instead, it uses its own archaic version due to legacy reasons. So if you try authenticating with the normal Tenant Id, the CF services will not be returned in the Service Catalog.

So one solution would be to introduce a new content option called `openstack.swift.tenantId` that has priority over `openstack.identity.tenantId`. If the former is not defined, the latter is used - therefore working for Rax and HP.