XENVBD #17 XENBUS #26

XENVBD
Fix BSOD caused by KeWaitForMultipleObjects()

XENBUS
Filter dbgprint logging more aggressively and provide a start option

Signed-off-by: Ben Chalmers <Ben.Chalmers@citrix.com>
Merge pull request #45 from benchalmers/vbd17bus26

XENVBD #17 XENBUS #26

Approved-By: Ben.Chalmers@citrix.com