TMF: Correction to the state system explorer to avoid AttributeNotFound

TMF: Correction to the state system explorer to avoid AttributeNotFound

The order of the state systems at creation is not the same as the order at
update, so a tree item was update with the wrong state system.

Change-Id: Ifa75109a1cfd7f47440bf364c11c56cc947a8523
Signed-off-by: Geneviève Bastien <gbastien+lttng@versatic.net>
Reviewed-on: https://git.eclipse.org/r/21589
Reviewed-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
IP-Clean: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Tested-by: Hudson CI