XenVif #44 and XenVbd #30

XenVif
    Change Cache lifecycle to match ring lifecycle.
	3714613096b1bb7b7a76e9d360106ea19208f243

XenVbd
    Increase PdoReset timeout and logging.
	16803a2321206ff7e7df71ebbed80b7120e96c09

Signed-off-by: Owen Smith <owen.smith@citrix.com>