Add a new function 'maybe_daemonize'

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Add the network interface

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Updates to the xenops interface

Fixes a problem with the barrier semantics and adds a new API
'VM.exists' that is more lightweight than 'VM.stat'

Signed-off-by: Jon Ludlam <jonathan.ludlam@eu.citrix.com>
Merge pull request #1 from jonludlam/xapi-updates

Updates to the xenops interface