bonding: do not cancel works in bond_uninit()

Bonding initializes these works in bond_open() and cancels in bond_close(),
thus in bond_uninit() they are already canceled but may be unitialized yet.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Nikolay Aleksandrov <nikolay@redhat.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: netdev@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>