Recent changes added SSL-level setters to these APIs. Unfortunately,
this has the side effect of breaking SSL_set_SSL_CTX, which is how SNI
is typically handled. SSL_set_SSL_CTX is kind of a weird function in
that it's very sensitive to which of the hodge-podge of config styles is
in use. I previously listed out all the config styles here, but it was
long and unhelpful. (I counted up to 7.)

Of the various SSL_set_SSL_CTX-visible config styles, the sanest seems
to be to move it to CERT. In this case, it's actually quite reasonable
since they're very certificate-related.

Later we may wish to think about whether we can cut down all 7 kinds of
config styles because this is kinda nuts. I'm wondering we should do
CERT => SSL_CONFIG, move everything there, and make that be the same
structure that is dropped post-handshake (supposing the caller has
disavowed SSL_clear and renego). Fruit for later thought. (Note though
that comes with a behavior change for all the existing config.)

Change-Id: I9aa47d8bd37bf2847869e0b577739d4d579ee4ae
Reviewed-on: https://boringssl-review.googlesource.com/13864
Reviewed-by: Martin Kreichgauer <martinkr@google.com>
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>