tmf: bug 517583 fix the experiment sync file path

tmf: bug 517583 fix the experiment sync file path

Commit 4b40a764980500b35c92f5a5da561905bbfcfcce removed the @Deprecated
public field containing the file name, but it just should have been made
private instead of removed.

Change-Id: Ie5fe921f98c56427ec3667184992d16f5bd169bd
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/98366
Reviewed-by: Hudson CI
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>