regression in bonding driver with VLAN challenged interfaces when 8021q module is loaded

Since commit cc0e40700656b09d93b062ef6c818aa45429d09a, there is a
problem if you have the 8021q module loaded and you then attempt to
enslave a VLAN challenged interface. This is because VLAN 0 is
automatically added to the bond, and the new bond_vlan_used() function
simply checks for an empty list in bond->vlan_list without taking into
account that VLAN0 might be on the interface.

This specifically affects IPoIB interfaces in a bond if you do a
down/up cycle on the bond post-boot (during boot, the bonding module
is loaded prior to the 8021q module, so everything is fine).

Let me know if further information or testing is needed.