selftests: mptcp: enhance userspace pm tests

Some userspace pm tests failed since pm listener events have been added.
Now MPTCP_EVENT_LISTENER_CREATED event becomes the first item in the
events list like this:

 type:15,family:2,sport:10006,saddr4:0.0.0.0
 type:1,token:3701282876,server_side:1,family:2,saddr4:10.0.1.1,...

And no token value in this MPTCP_EVENT_LISTENER_CREATED event.

This patch fixes this by specifying the type 1 item to search for token
values.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>