bonding: make ab_arp select active slaves as other modes

When I was implementing primary_passive option (formely named primary_lazy) I've
run into troubles with ab_arp. This is the only mode which is not using
bond_select_active_slave() function to select active slave and instead it
selects it itself. This seems to be not the right behaviour and it would be
better to do it in bond_select_active_slave() for all cases. This patch makes
this happen. Please review.

Signed-off-by: Jiri Pirko <jpirko@redhat.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>