This fixes the RCU race on bridge delete interface.  Basically,
the network device has to be detached from the bridge in the first
step (pre-RCU), rather than later. At that point, no more bridge traffic
will come in, and the other code will not think that network device
is part of a bridge.

This should also fix the XEN test problems.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>