selftests: mptcp: join: no RST when rm subflow/addr

commit 2cfaa8b3 upstream.

Recently, we noticed that some RST were wrongly generated when removing
the initial subflow.

This patch makes sure RST are not sent when removing any subflows or any
addresses.

Fixes: c2b2ae39

 ("mptcp: handle correctly disconnect() failures")
Cc: stable@vger.kernel.org
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231018-send-net-20231018-v1-5-17ecb002e41d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>