BUG/MEDIUM: session: fix FD leak when transport layer logging is enabled

BUG/MEDIUM: session: fix FD leak when transport layer logging is enabled

Commit 2b199c9a attempted to fix all places where the transport layer
is improperly closed, but it missed one place in session_free(). If
SSL ciphers are logged, the close() is delayed post-log and performed
in session_free(). However, conn_xprt_close() only closes the transport
layer but not the file descriptor, resulting in a slow FD leak which is
hardly noticeable until the process cannot accept any new connection.

A workaround consisted in disabling %sslv/%sslc in log-format.

So use conn_full_close() instead of conn_xprt_close() to fix this there
too.

A similar pending issue existed in the close during outgoing connection
failure, though on this side, the transport layer is never tracked at the
moment.