bonding: fix enslavement error unwinds

	As part of:

commit c2edacf8
Author: Jay Vosburgh <fubar@us.ibm.com>
Date:   Mon Jul 9 10:42:47 2007 -0700

    bonding / ipv6: no addrconf for slaves separately from master

two steps were rearranged in the enslavement process: netdev_set_master
is now before the call to dev_open to open the slave.

	This patch updates the error cases and unwind process at the
end of bond_enslave to match the new order.  Without this patch, it is
possible for the enslavement to fail, but leave the slave with IFF_SLAVE
set in its flags.

Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>