tmf: some updates to the statistics

tmf: some updates to the statistics

- Changes the statistics node reset behavior to avoid useless
operations;
- Removes unused messages;
- Updates some javadoc;

Change-Id: I5af35217a711cdce06807929c4621dfb88cd2fa1
Signed-off-by: Mathieu Denis <mathieu.denis@polymtl.ca>
Reviewed-on: https://git.eclipse.org/r/7333
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
IP-Clean: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-by: Bernd Hufmann <bhufmann@gmail.com>
IP-Clean: Bernd Hufmann <bhufmann@gmail.com>
Tested-by: Bernd Hufmann <bhufmann@gmail.com>