The existing TLS probe is documented to ignore SSL 2.0, citing RFC 6176 as a reason.
RFC 6176 does prohibit the usage of SSL 2.0, but does allow for ClientHello messages
in the version 2 CLIENT-HELLO format (as long as those are used to negotiate the use
of a higher protocol).
This commit extends the TLS probe, by making it accept SSL v2 ClientHello messages
that negotiate a version of SSL/TLS 1.0 or higher (which is the same version range
as the original code).
