openssl: remove conn->data use

openssl: remove conn->data use

We still make the trace callback function get the connectdata struct
passed to it, since the callback is anchored on the connection.

Repeatedly updating the callback pointer to set 'data' with
SSL_CTX_set_msg_callback_arg() doesn't seem to work, probably because
there might already be messages in the queue with the old pointer.

This code therefore makes sure to set the "logger" handle before using
OpenSSL calls so that the right easy handle gets used for tracing.

Closes #6522