Return all matching roles in NodeObject#active if bc instance is nil
Merge pull request #867 from bkutil/add_wildcard_to_active_role_search

Return all matching roles in NodeObject#active if bc instance is nil
Also add Support for Xen Virtual Disks (/dev/xvd*)
Merge pull request #868 from vuntz/xvd

Also add Support for Xen Virtual Disks (/dev/xvd*)