selftests: mptcp: fix fastclose with csum failure

Running the mp_join selftest manually with the following command line:

  ./mptcp_join.sh -z -C

lead 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: Reported-by: Xiumei Mu <[email protected]>
Fixes: ("6bf41020b72b selftests: mptcp: update and extend fastclose test-cases")
Signed-off-by: Paolo Abeni <[email protected]>

tools/testing/selftests/net/mptcp/mptcp_join.sh

@@ -3220,7 +3220,7 @@ fastclose_tests()
 	if reset_check_counter "fastclose server test" "MPTcpExtMPFastcloseRx"; then
 		test_linkfail=1024 fastclose=server \
 			run_tests $ns1 $ns2 10.0.1.1
-		chk_join_nr 0 0 0
+		chk_join_nr 0 0 0 0 0 0 1
 		chk_fclose_nr 1 1 invert
 		chk_rst_nr 1 1
 	fi