Fix: output number of bytes written by relayd

The print of the number of bytes written in the tracefile by the relayd
was after the call to write the padding, so the debug output was
confusing:

DEBUG3: Receiving data of size 2097133 for stream id 567 seqnum 0 [in
relay_process_data() at main.c:1394]
DEBUG2: Relay wrote 19 bytes to tracefile for stream id 567 [in
relay_process_data() at main.c:1416

Signed-off-by: Julien Desfossez <jdesfossez@efficios.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>