MINOR: quic: Set the QUIC connection as extra data before calling SSL_set_quic_method()

MINOR: quic: Set the QUIC connection as extra data before calling SSL_set_quic_method()

This patch is required for the QUIC OpenSSL wrapper, and does not break anything
for the other TLS stacks with their own QUIC support (quictls for instance).

The implementation of SSL_set_quic_method() needs to access the quic_conn object
to store data within. But SSL_set_quic_method() is only aware of the SSL session
object. This is the reason why it is required to set the quic_conn object
as extra data to the SSL session object before calling SSL_set_quic_method()
so that it can be retrieve by SSL_set_quic_method().