After the commit 5ce2dced8e95 ("RDMA/ipoib: Set rtnl_link_ops for ipoib
interfaces"), if the IPoIB device is moved to non-initial netns,
destroying that netns lets the device vanish instead of moving it back to
the initial netns, This is happening because default_device_exit() skips
the interfaces due to having rtnl_link_ops set.
Steps to reporoduce:
ip netns add foo
ip link set mlx5_ib0 netns foo
ip netns delete foo
To avoid the above warning and later on the kernel panic that could happen
on shutdown due to a NULL pointer dereference, make sure to set the
netns_refund flag that was introduced by commit 3a5ca857079e ("can: dev:
Move device back to init netns on owning netns delete") to properly
restore the IPoIB interfaces to the initial netns.