[PATCH net-next v3 0/6] rtnetlink: preparation patches for further rtnl lock pushdown/removal

First patch adds a rudimentary vrf test case.

Remaining patches split large rtnl_fill_ifinfo into smaller chunks
to better see which parts

1. require rtnl
2. do not require it at all
3. rely on rtnl locking now but could be converted

I removed all the ASSERT_RTNL spots that v1 and v2 added,
i will keep that back in my working branch since those
are just 'todo' markers for myself.

Eric Dumazet pointed out that qdiscs are now freed directly without
call_rcu so I dropped the patch that made this assumption from the series.

As the remaining patches did not see major changes vs. v2 I retained
all reviewed/acked-by tags from David Ahern.