vtls: fix ssl version "or later" behavior change for many backends

- Treat CURL_SSLVERSION_MAX_NONE the same as
  CURL_SSLVERSION_MAX_DEFAULT. Prior to this change NONE would mean use
  the minimum version also as the maximum.

This is a follow-up to 6015cefb which changed the behavior of setting
the SSL version so that the requested version would only be the minimum
and not the maximum. It appears it was (mostly) implemented in OpenSSL
but not other backends. In other words CURL_SSLVERSION_TLSv1_0 used to
mean use just TLS v1.0 and now it means use TLS v1.0 *or later*.

- Fix CURL_SSLVERSION_MAX_DEFAULT for OpenSSL.

Prior to this change CURL_SSLVERSION_MAX_DEFAULT with OpenSSL was
erroneously treated as always TLS 1.3, and would cause an error if
OpenSSL was built without TLS 1.3 support.

Co-authored-by: Daniel Gustafsson

Fixes https://github.com/curl/curl/issues/2969
Closes https://github.com/curl/curl/pull/3012