NetworkManager likes to manage linklocal prefix routes and does so with
the NLM_F_APPEND flag, breaking attempts to simplify the IPv6 route
code and by extension enable multipath routes with device only nexthops.
Revert f34436a430 and these followup patches:
6eba08c362 ("ipv6: Only emit append events for appended routes").
ce45bded64 ("mlxsw: spectrum_router: Align with new route replace logic")
53b562df8c ("mlxsw: spectrum_router: Allow appending to dev-only routes")
Update the fib_tests cases to reflect the old behavior.
Fixes: f34436a430 ("net/ipv6: Simplify route replace and appending into multipath route")
Signed-off-by: David Ahern <dsahern@gmail.com>
33bd5ac54d