Merge branch 'selftests/bpf: use temp netns for testing'

Hangbin Liu says:

====================

There are some bpf tests using hard code netns name like ns0, ns1, etc.
This kind of ns name is easily used by other tests or system. If there
is already a such netns, all the related tests will failed. So let's
use temp netns name for testing.

The first patch not only change to temp netns. But also fixed an interface
index issue. So I add fixes tag. For the later patches, I think that
should be an update instead of fixes, so the fixes tag is not added.
====================

Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>