selftests: mptcp: update userspace pm addr tests

selftests: mptcp: update userspace pm addr tests

This patch is linked to the previous commit ("mptcp: only send RM_ADDR in
nl_cmd_remove").

To align with what is done by the in-kernel PM, update userspace pm addr
selftests, by sending a remove_subflows command together after the
remove_addrs command.

Fixes: d9a4594edabf ("mptcp: netlink: Add MPTCP_PM_CMD_REMOVE")
Fixes: 97040cf9806e ("selftests: mptcp: userspace pm address tests")
Cc: stable@vger.kernel.org
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>