libnl

route: treat nhid changes as full route replacements

tests: skip various tests when kernel returns EOPNOTSUPP (NLE_OPNOTSUPP)

tests: add and use _nltst_skip_eopnotsupp() helper

error: revert mapping EHOSTUNREACH/ENETDOWN

route/nh: don't refer to the "resvd{1,2}" fields in nexthop_grp