have carp use standard detach hooks instead of getting special handling

have carp use standard detach hooks instead of getting special handling

if_deactivate looked for carp parent interfaces and called carp_ifdetach
to have children interfaces unplug themselves. this diff has the
carp interfaces register detach hooks on the parent instead. the
effect is the same, but using the standard every other interface
uses.

while im here i shuffle the order the hooks carp_set_ifp are
estabilshed so it will fail if they arent allocated.

ok visa@ mpi@