Illumos regtest: add an expected for none/tests/fdleak_socketpair_xml.stderr

Illumos regtest: add an expected for none/tests/fdleak_socketpair_xml.stderr

illumos socketpair doesn't get the next two fds (3 and 4), instead it
gets 4 and 5. That looks like it's because this is done in two steps in libc.
so_socket gets called twice returnning fds 3 and 4 the so_socketpair takes
those and does some rebinding(?) resulting in fds 4 and 5.