tests: shorten names of session-rotation trace

tests: shorten names of session-rotation trace

Filenames of this trace on the CI are too long for Windows, causing test
failures.  Shorten some directory names to avoid that

Change-Id: I8d936af3efca894d55a94a57e3a3d4d5b0441305
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8694
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-by: Michael Jeanson <mjeanson@efficios.com>
(cherry picked from commit 8dea686a2397bdadb81f44a3e74fd39fd7397ee2)
Reviewed-on: https://review.lttng.org/c/babeltrace/+/9549
Tested-by: jenkins <jenkins@lttng.org>