Only call ifa_del() when no error happend previously. Do the same thing for dohooks() since it makes no sense to call the if_addrhooks when the address assignment failed. Additionally only call ifa_add() in in_ifinit() when no error happend. Fixes a carp(4) panic seen by dhill and dlg.  OK henning@, dlg@
Only call ifa_del() when no error happend previously. Do the same thing
for dohooks() since it makes no sense to call the if_addrhooks when the
address assignment failed. Additionally only call ifa_add() in
in_ifinit() when no error happend. Fixes a carp(4) panic seen by dhill
and dlg.  OK henning@, dlg@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars