Fix enable-ssl3 enable-ssl3-method

Commit 4aa5a566

 accidentally missed off the catch all case of ignoring all
warning alerts that are otherwise unhandled. This breaks the SSLv3 tests
which send a "no certificate" warning alert.

Fixes #6496

[extended tests]

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/6509)