ctf: decoding: accommodate LTTng `event-after-packet` timestamp quirk

ctf: decoding: accommodate LTTng `event-after-packet` timestamp quirk

See prior commit titled:
  src.ctf.fs: index: accommodate bug in LTTng tracers
for an explanation of the non-compliance of some LTTng traces.

How this commit fixes the decoding for the affected traces
==========================================================
When about to emit a packet end message, check if the said packet is
affect by LTTng's `event-after-packet` bug. If it's the case, omit to
update the default_clock_snapshot to the `timestamp_end` of the packet.
This will expand the packet time span to the contain all its events.

Signed-off-by: Francis Deslauriers <francis.deslauriers@efficios.com>
Change-Id: I205caf0243c1d6f270bdb1b6508bb55a0806ba19
Reviewed-on: https://review.lttng.org/c/babeltrace/+/1550
Tested-by: jenkins <jenkins@lttng.org>
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>