vif script: look for bridge in backend/vif/<domid>/<devid>/bridge first

This is where libxl puts it. We fall back to the "private" location if not
there.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xl: merge in device_common and hotplug changes from xc

This includes changes to support blktap3 (note that blktap3 would still need
changes in libxl if we want to use it).

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xl: write bridge-MAC

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
vif-real: log UUID

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xc: move no-physical-device xs key to private (as in xl)

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xl: use classic hotplug scripts

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Merge pull request #107 from robhoes/vif-xl

Merge hotplug scripts for xenopsd classic and libxl