For pppoe/ng interfaces sometimes we enter ip6_tryforward() with
a NULL pointer array and IN6_LINKMTU() glancing over the fact
that this is not a valid destination since if_afdata structure
is not initialized.
While here remove the RT_LINK_IS_UP macro since nothing outside
of nhop is using it.
This is probably a side effect generator, but fixing one spot
instead of the general case would leave other holes in the stack.
Do not return a route destination if the address families were not
yet attached.
5dc500ba7a