TS_SSL_SNI_HOOK correspond to the same openssl
callbacks. This is done for backwards compatibility.
TS_SSL_SNI_HOOK is expected
to be deprecated and removed, plugins using this should change to
TS_SSL_SERVERNAME_HOOK as appropriate.
openssl 1.0.2 and later versions
TS_SSL_SERVERNAME_HOOK is invoked for the openssl servername callback.
TS_SSL_CERT_HOOK are invoked for the openssl certificate
callback which is not guaranteed to be invoked for a TLS transaction.
This is a behavior change dependent on the version of openssl. To avoid problems use
TS_SSL_SERVERNAME_HOOK to get called back for all TLS transaction and
TS_SSL_CERT_HOOK to get called back only to select a certificate.