tmf: Move creation of timer to init method instead of constructor

tmf: Move creation of timer to init method instead of constructor

By the doing this, the timer is not running when creating trace
instances for validation.

Also, cancel timer when trace is disposed.

Change-Id: I4269ddb1faba771c039649d92f2e1477076668c8
Signed-off-by: Bernd Hufmann <Bernd.Hufmann@ericsson.com>
Reviewed-on: https://git.eclipse.org/r/21138
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
IP-Clean: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Hudson CI