selftests: mptcp: fix fastclose with csum failure

[ Upstream commit 7cefbe5e

 ]

Running the mp_join selftest manually with the following command line:

  ./mptcp_join.sh -z -C

leads to some failures:

  002 fastclose server test
  # ...
  rtx                                 [fail] got 1 MP_RST[s] TX expected 0
  # ...
  rstrx                               [fail] got 1 MP_RST[s] RX expected 0

The problem is really in the wrong expectations for the RST checks
implied by the csum validation. Note that the same check is repeated
explicitly in the same test-case, with the correct expectation and
pass successfully.

Address the issue explicitly setting the correct expectation for
the failing checks.

Reported-by: Xiumei Mu <xmu@redhat.com>
Fixes: 6bf41020

 ("selftests: mptcp: update and extend fastclose test-cases")
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20231114-upstream-net-20231113-mptcp-misc-fixes-6-7-rc2-v1-5-7b9cd6a7b7f4@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>