Make the Boring tests pass

The boring tests are currently failing because they send a PSK extension
which isn't in the last place. This is not allowed in the latest TLS1.3
specs. However the Boring tests we have are based on an old commit that
pre-date when that rule first appeared.

The proper solution is to update the tests to a later commit. But for now
to get travis to go green we disable the failing tests.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/2928)