ksmbd: fix multichannel connection failure

[ Upstream commit c1883049 ]

ksmbd check that the session of second channel is in the session list of
first connection. If it is in session list, multichannel connection
should not be allowed.

Fixes: b9562943 ("ksmbd: fix racy issue from session lookup and expire")
Reported-by: Sean Heelan <seanheelan@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>