ctf: change logging of raw packet data to TRACE level

This logging statement is very noisy. Even if the packet is mostly
empty, the logging statement will print ~120 lines of 0x00 bytes.

For example:

  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 c11ffcc12a8a00ec460a46f1818701327971f76a000000001400000000000000  ????*???F?F????2yq?j????????????
  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 d2e48fbadb1c070047ce81f7db1c0700a0020000000000000080000000000000  ????????G???????????????????????
  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 0000000000000000000000000000000014000000000000000000000000000000  ????????????????????????????????
  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 0000000000000000000000000000000000000000000000000000000000000000  ????????????????????????????????
  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 0000000000000000000000000000000000000000000000000000000000000000  ????????????????????????????????
  11-11 18:29:32.493 59609 59609 D PLUGIN/CTF/MSG-ITER request_medium_bytes@msg-iter.c:510 0000000000000000000000000000000000000000000000000000000000000000  ????????????????????????????????
  ...

This commit changes the log-level of this statement to TRACE.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: Idd3fc655f2fffc77130a7898ef94e7c117bcd9ec
Reviewed-on: https://review.lttng.org/c/babeltrace/+/6705
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>