Merge branch ' bpf fix for unconnect af_unix socket'

John Fastabend says:

====================
Eric reported a syzbot splat from a null ptr deref from recent fix to
resolve a use-after-free with af-unix stream sockets and BPF sockmap
usage.

The issue is I missed is we allow unconnected af_unix STREAM sockets to
be added to the sockmap. Fix this by blocking unconnected sockets.

v2: change sk_is_unix to sk_is_stream_unix (Eric) and remove duplicate
    ASSERTS in selftests the xsocket helper already marks FAIL (Jakub)
====================

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>