need to ensure we cover all of the below combos with our connectivity (ping) suites.
>
> compute-a                  compute-b
> ---------------------      -----------------------
> all vlan, all vxlan        none
> all vlan                   all vxlan
> some vlan, all vxlan       some vlan
> all vlan, some vxlan       some vxlan
> some vlan, some vxlan      some vlan, some vxlan

there was some combos that sometimes had a bug, and we were seeing them
sporadically when nova was randomly scheduling which compute was getting
which instance. That was fixed by being explicit about where we want nova to
place each instance. But, now we are never testing certain combinations and we
need to ensure they are all covered.

This might be best to do the work in each of the three connectivity suites (l2, l3 and
external) just to be safe