Don't raise 404 when deleting a server because it doesnt have a schedule

Change-Id: Iae96d9af3e3bc4bd11c37c91fb907592e00374c9
Merge pull request #32 from rackspace-titan/extension-OS-SI-del-server

Don't raise 404 when deleting a server because it doesnt have a schedule
uses the tenant from context object instead of req
Merge pull request #33 from rackspace-titan/extension-OS-SI-tenant-id

uses the tenant from context object instead of req
pep8 fix