bonding: re-evaluate force_primary when the primary slave name changes

There is a timing issue under active-standy mode, when bond_enslave() is
called, bond->params.primary might not be initialized yet.

Any time the primary slave string changes, bond->force_primary should be
set to true to make sure the primary becomes the active slave.
Signed-off-by: Xiangning Yu <yuxiangning@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_options.c

@@ -1142,6 +1142,7 @@ static int bond_option_primary_set(struct bonding *bond,
 				   slave->dev->name);
 			rcu_assign_pointer(bond->primary_slave, slave);
 			strcpy(bond->params.primary, slave->dev->name);
+			bond->force_primary = true;
 			bond_select_active_slave(bond);
 			goto out;
 		}