SSL: adopted session ticket handling for OpenSSL 1.1.0.

Return 1 in the SSL_CTX_set_tlsext_ticket_key_cb() callback function
to indicate that a new session ticket is created, as per documentation.
Until 1.1.0, OpenSSL didn't make a distinction between non-negative
return values.

See https://git.openssl.org/?p=openssl.git;a=commitdiff;h=5c753de for details.