TLS crash after reconnect

Both OpenSSL and GnuTLS need to retrieve the MYSQL connection handle in case of an error via gnutls_session_get_ptr() or SSL_get_app_data() api functions.

In case an reconnect occurred, the returned pointer still points to the stack address of tmp_mysql structure, declared in mariadb_reconnect() function. Since the content of tmp_mysql is copied to mysql, it is also necessary to update the mysql handle via gnutls_session_set_ptr() or SSL_set_app_data().