[Common] Fix stale Q/Pt values in TrackTuner graph-based smearing

[joonsukbae]

@mfaggin,

When qOverPtMC and qOverPtData are configured as negative sentinels (requesting graph-based evaluation), the original code overwrites the member variables on the first track call. All subsequent tracks then skip graph evaluation and reuse stale values from the first track's pT, applying incorrect smearing.

Fix: use local variables (currentQOverPtMC, currentQOverPtData) so each track evaluates the graphs at its own pT. The member variable sentinels remain negative, ensuring graph evaluation on every call.

[mfaggin]

Many thanks @joonsukbae , indeed as in the code now the usage of the graph is not ok for the issue you said. Apologize, this option was just tested locally one time, and it is not really used, so you are the first real deep user.

Your solution looks ok to me, I just ask you to change the variable names since "current" is a word that internally we use for the MC, i.e. the "current" values to be "upgraded".

[mfaggin]

Suggested change

	double currentQOverPtMC = qOverPtMC;
	double currentQOverPtData = qOverPtData;
	if (updateCurvature || updateCurvatureIU) {
	double smearQOverPtMC = qOverPtMC;
	double smearQOverPtData = qOverPtData;
	if (updateCurvature || updateCurvatureIU) {