Update for blktap:
    - Workaround blktap/xenstore startup race
    - Add udev rules for xen blktap devices (srostedt)
    - Add support for dynamic blktap device nodes (srostedt)
    - Fixes for infinite dom0 cpu usage with blktap
    - Fix xm not to die on malformed "tap:" blkif config string
    - Enable blktap on kernels without epoll-for-aio support.
    - Load the blktap module automatically at startup
    - Reenable blktapctrl